Hey, two more quick things:
The third party iOS app is called Watt. I’m not routinely using it. I only went looking for it in an attempt to troubleshoot the issue. I’ve since removed it from my devices.
I have to unplug and re-plug each KP115 in oder to make them visible in the Sense again. They come back one by one.
I beginning to thing you are correct. I wonder why Sense does not use the Kasa cloud or Multicast?
This has been happening every few/several days with three different wireless systems. First an all Apple Extreme (three hardwired units in AP only mode), then with just the Sense and KP115’s alone on the Verizon Fios router’s built in WIFI and now finally on a Netgear three unit Orbi WIFI 6 mesh system.
The only common piece is the Verizon FIOS router which is the main router.
I’ve had the same problem with my KP115’s (now 5 of them). I wrote a thread about it, if you want to read some details. My experience is exactly like @Offthewall in that they all go out at the same time, they stay out until you unplug/replug them, and yet the Kasa app never has any trouble reading them. My LAN is a TP-Link Deco M9+ router (mesh system), sitting behind an AT&T fiber cable modem. I have found that rebooting the router will also bring them back in Sense.
Yes, I would agree you have EXACTLY the same issue as I do. I have an open ticket with Sense but have not heard back in awhile.
Since we have different networks, routers, WIFI systems and I personally have had three different WIFI systems, it seems unlikely these are isolated cases. Something is amiss with Sense/KP115 communication under some repeating unknown circumstances. Or is the magic number 5???
I wish someone at Sense could look closely at our two cases and try to find the common denominator.
In the meantime, I’ll keep running around the house unplugging them once a week or so. I’ve got to relocate one to make that a little easier on my back. 
@Offthewall @demiller9 I believe further investigation on this dropped off after it was attributed to a network issue instead of a Sense issue, but I’ll talk to some folks internally and see if we can get any more information for you here.
So far, the feedback from @dennypage regarding where the issue could be is spot on from our best guess is right now.
That they come back individually effectively eliminates the possibility that Sense is has stopped sending the broadcast packet or is ignoring responses from the plugs.
To save your back, you might try sending a reboot command to the plug instead. There is a command script written by the guy who did the original reverse engineering of the tplink protocol:
I would counter that it’s likely Sense not dealing properly with a normal but relatively uncommon network “situation”. 
I’ve dug through the threads and there are at least two others besides @demiller9 and myself who have experienced this exact issue. It’s often been confused with zero or sub .5 w power draws showing the KP115 as OFF. This is not what’s happening here. Sense is loosing communication completely with all KP115s simultaneously. That communication is never reestablished until the KP115s are power cycled. During the loss of communication, all KP115s continue to report to and can be controlled by the Kasa app.
Both of us are using mainstream consumer products as our network infrastructure. I’ve read the various possible reasons of the sense packets being dropped because of a network error etc. That seems like sketchy reasoning. The Sense tries once and if no response never again?
The assertion that Sense is “tries once” isn’t correct. If TP-Link Smart Plug integration is turned on, Sense sends the broadcast query even if there is no one to hear it. This is how the smart plug discovery works. Further, the fact the smart plugs re-appear one by one when they are rebooted is evidence that Sense is continuing to send the broadcast query.
This leaves two possibilities: 1) the plug, 2) the network infrastructure. Given that all plugs disappear simultaneously, option 1 is pretty unlikely. Option 2 is the clear winner. Given that this is all based on broadcast, and broadcast implementations are pretty flakey these days, this makes a lot of sense.
Yes, Sense could use broadcast for discovery (just as the Kasa app does), and then use point to point to poll data values which would be more reliable. Unfortunately, this breaks down unless the plug has a statically assigned IP address, which most home networks don’t use. Multicast would be a better choice for all of this, but to the best of my knowledge the plugs don’t support multicast.
In essence, Sense doesn’t have any effective local network option other than what they are currently doing.
@Offthewall Unlikely the issue, but do you use any 3rd party DNS servers? What common elements do you have on your network before and after you switched to Orbi? Modem in bridge mode?
There’s a lot of brainpower in the forums, I’m sure there is a logical explanation. I also have several KP115s and about 30 HS110s, they stay online unless I screw something up!
Based on what @Offthewall stated earlier, the only common element, over the 3 different network implementations that show this issue, is the FIOS modem, router, WiFi, switch combo. But I forget if he only has KP115s or has other Kasa models that aren’t seeing the same issue.
I have had a pair of HS300s go offline from Sense in a similar manner to @Offthewall s KP115, but only very infrequently (maybe once per year). It has me wondering whether the Sense monitor blacklists a reporting Kasa device if the device reporting becomes too erratic for some period of time. That could be a legitimate protective mechanism if the Sense monitor tries to fill / error correct the inevitable missing responses from various smart plugs.
Appreciate your question about third party DNS because there can be unintended consequences from using those. A few years ago, I tried using Google’s DNS servers and my OTP video streaming became incredibly slow. Turns out using a third party DNS server had confused the streaming services CDN, so the video was being sent from a network distribution point “far removed” from my house.
The FIOS modem/router combo and a Netgear 48port managed switch are the only common network infrastructure elements. The FIOS box is only used as a modem/router with a single GB Ethernet connection from the ONT and a single Ethernet connection to the 48 port switch. The FIOS WIFI is shut off except for a brief experiment when I had just the Sense and KP115’s alone on it’s internal WIFI - otherwise I do not use the WIFI of the FIOS box. The 48 port switch has been defaulted to stock condition and there are no rules in it at all - acting as a dumb switch.
I do not have any other Kasa products, just the five KP115s.
I do use Google’s DNS servers, set in the FIOS router.
FWIW, default configurations on these types of switches do not usually act as pure dumb switches. They often have “smart” features like broadcast filtering or storm control enabled by default. Similar approaches are taken by most wifi AP makers.
Questions:
The WIFI system currently is a three unit Netgear Oribi WIFI 6 mesh system. Model AX6000 RBK853. One main wired unit and two dedicated 5GHz backchannel connected satellites in AP mode (no routing).
The switch is a Netgear GS748Tv4H2.
The Sense and one of the plugs are on one Satellite, the other 4 plugs are on the main Orbi unit due to their locations in the house. That traffic between AP’s does not go through the switch but rather the Orbi dedicated 5GHz backchannel.
The FIOS router is providing DHCP. Yes I can configure static IPs.
I assume your firmware is up to date for all the Orbis. I took a look at the manual for Orbi. Not much they let you get at, but you do want to ensure that both the firewall and QoS are disabled for all three of the units.
On the DHCP front, make absolutely sure that there is one and only one device in the network serving DHCP.
And while I doubt it will address your problem, you might consider making static assignments for all the devices involved (Sense and all the plugs). Just in case the infra is getting confused when addresses change. Note that the new address assignments will generally not take effect until devices are restarted.
HTH
Thanks.
The Orbi’s are up to date firmware wise. They are in AP mode, so there is no firewall, router or QOS functions.
There is definitely only one DHCP server, the FIOS router.
I will try assigning static IP’s to sense and the kp115s.
Are you completely sure about this? Maybe I misunderstood the manual, but given that the satellites are documented as having their own firewall settings separate than that of the routing node, I would have expected that the firewall setting is active even in AP mode. Many APs offer limited firewall capabilities.
The QoS setting is explicitly documented in the Orbi manual as being for QoS on the wifi links. This should be irrespective of routing vs AP mode–if it only applied in routing mode it would be a serious implementation defect. Most APs offer QoS which is disabled by default, but the Orbi manual says it is enabled by default. Wifi QoS “optimizations” can easily be the source of unexpected side effects (or outright bugs).
Absolutely no firewall settings in AP mode. That area get grayed out when you enable AP mode. As far as QOS, I do not see any pages for that in the web interface in either Router or AP mode
I don’t have any direct experience with Orbi. However, the user manual located in “RBK853 Orbi WiFi 6 System AX6000 Documentation” located here:
describes the setting in the user manual, chapter 5, page 51. The setting is purportedly under ADVANCED>Advanced>WirelessSettings. There is a separate setting for each radio. Enabled by default for both radios.
HTH
Ha, I was just coming back here to mention I found that exact page. 
I turned off the WMM (Wi-Fi multimedia) settings (2.4GHz b/g/n/ax). We’ll see if that helps. I’m certainly not running any multimedia streams on the 2.4GHz band.
