Where the main wires come into from your street, do you know if it’s a single 400A line that is split into 2 feeds in one of those boxes below the panels? If it’s a single feed that simply splits before the panels then you just need to find the single main incoming line and hookup your sense there to aggregate the entire incoming feed.
If you do indeed have 2 fully separate 200A feed wires coming straight from your street hookup, then there’s no way you’re going to be able to use a single unit unfortunately.
Also take note that Sense isn’t officially supported for more than 200A services so although I will say that others have done so (here’s just one thread detailing such) it’s technically not supported at this point. But it seems to work OK, with caveats.