Chevy Volts are regularly detected. Check out the available threads. Here’s a Volt-specific one, with images; Electric Vehicle - 2017 Chevy Bolt EV - #3 by markhovis73
And here’s the massive (over 450 posts) omnibus EV detection thread: Detecting Electric Vehicle (EV) devices
The short version is EVs require specific usage models for each model of EV, and the Volt is one that has such a model created for it. It took between 1 and 2 months of charging 4-6 times a week for my Leaf to be detected once the usage model was available. Make sure you perform a full charge cycle each time, and be patient, and your Volt should be detected.