I have two houses with very similar HA installations. Zigbee2mqtt plugin has 100% same config. Both HAs has CC2531 USB stick, both Zigbee networks work fine.
I built Zigbee router exactly as described here: https://www.zigbee2mqtt.io/how_tos/how_to_create_a_cc2530_router.html
And there is problem - router works absolutely fine in house A but not work in house B. In house A after few seconds after power up i have log message about router and zigbee map shows connected router. After power up in house B nothing happened.
WHY? How to investigate where is problem?