Suddenly Stopped Working

Not sure what happened. I initially purchased one for my bathroom to pair with my SmartThings and, after working great, I purchased another for my other bathroom. After a few weeks, both suddenly stopped working. I've tried taking the battery our of the sensors and removing them from SmartThings as well. Nothing. SmartThings no longer detects them. Maybe it's just my system, but these are useless for me now.

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