I highly recommend that you start by reading and try following all the tips in this guide before you troubleshoot further or dig into debug logs any deeper → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Zigbee radios is relatively speaking extremely sensitive to EMF interference from close sources (at least within 1-2 meters) + Zigbee devices have very poor range relatively speaking and therefore depends heavily on its mesh networking technology which only works oif you have many Zigbee Router devices to extend range and coverage.