Try a reset, re-pair using the following steps:
1.Remove the white cover
2. Select the “three white dots” on the top right of the Home Screen
3. Connect New Device
4. + Connect Now
5. Hold down the white button for six seconds, until the green light goes out
6. Press the white button for two seconds, repeat this six times. The continuously forces the presence tag into pairing mode
It may take several minutes to pair, if it doesn’t pair, there is chance it has already paired in the back ground. Press the top left back arrow, next to “Connect Now” At the top of the new menu it may say “1 device unconfirmed” click this tab, then name the presence tag, then save. The device should then appear under your things tab and should hopefully start working again