ConBee III (ConBee 3) from Dresden-Elektronik based on Silicon Labs EFR32MG21 +20dBm radio SoC/MCU

It should work if using the ZHA integration in the latest Home Assistant, (or at the very least be able to pair/join Zigbee devices if you have a proper setup in a good environment), so first make sure that you have already followed all these tips before troubleshooting any deeper → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage

It should then be to just use best practices (which assume you done above) → https://www.home-assistant.io/integrations/zha/#best-practices-to-avoid-pairingconnection-difficulties