Please be specific, restarting Homey does not solve stuff a PtP (leave it unplugged for 10 - 15 minutes) can.
This question by Dirk is asked for a reason:
When the sensors are the first zigbee devices you’d like to add, consider resetting zigbee.
First set your 2.4GHz wifi channel to either 1, 6 or 11.
Why?
https://community.homey.app/t/advanced-zigbee-troubleshooting-on-homey/115930
Note: I had to reset zigbee 4 times until I could add devices.
