Stop/start option is not working?

The battery might be fully charged but it may be getting weak, and the sensor can tell this, let's try a battery load test, please follow this guide or remove the battery and take it to an auto parts store for testing:

https://www.2carpros.com/articles/car-battery-load-test

If the battery tests good let's run a CAN scan to see what codes are stored. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Also, let's check the fuses, here is guide that can help and I have included the starter wiring diagrams so you can see how the system works and which fuses to test, also there are two starter relays I would try to swap out to see if that makes a difference.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.