Hey, @CTreb-1551!
I have seen this issue before. Usually I believe it's related to devices that just learned the seatbelt logic incorrectly. My recommendation is that you uninstall the devices, unplug them and plug them back in twice (pretty sure twice resets the internal logic), and drive them around a bit. The devices "learn" what state a seatbelt is in as you go, so if the vehicle is turned on and the device is plugged in and then you engage the seatbelt before driving, keep it on while driving, and disengage once driving is over, that should help it learn what states are correct. You may want to do this two or so times to make sure things look like they're reading properly.
If that doesn't work, I'd recommend filing a ticket with Geotab Support or your reseller--whichever is your usual support channel--so they can take a closer look. The in-cab lights (mechanical) don't necessarily correspond with the data the engine is sending (digital), and I suppose it's possible that the engine could actually be sending the opposite signal. This is a less likely case, I think, but figured I'd mention it in case it gives you something to rule out if the first set of tests doesn't work.
Anyway, hope this helps. :)
Best,
Joy B