It is possible that the motion sensor has gone bad. Have you checked the contact sensors to see if they are working properly? If the other sensors are working, it could be a problem as you said with the motion sensor alone.
First thing comes to mind after changing the battery:
- Check battery orientation
From Troubleshooting Section
If the sensor doesn’t start working again after replacing the battery, check to make sure that the battery is placed in the correct orientation (the positive side(+) should be visible after the battery is inserted), and is fully seated.
If the battery is in correctly, then I would recommend contacting support about this issue. Go to the Wyze app, > Go to Account > Help & Feedback > Report an Issue. Then you will get a support ticket number in your email.