This fixed it for me too, apparently USB 3.0 uses 2.4GHz internally which causes a lot of interference, did not know this.
I just experienced the same issue, so thought I’d mention what I needed to do to fix it as it was a bit different to what others have mentioned.
My HA runs on a Promox VM server / mini PC.
HAOS 9.5
HA Core 2023.3.1
(guess I should update soon)
I had a new data access point installed, which on its own is unrelated to the ZHA and Zigbee network but the work required shutting down power to the home for safety reasons as the cable guys were working in the ceiling cavity. So the HA server was powered down.
Once the work was all done and the home power restored, I got all my regular stuff back online and working, except for the Zigbee network - the ZHA integration just refused to load.
I would get the following error in the log:
Error setting up entry ConBee II for zha
10:11:08 AM – (ERROR) components/zha/core/gateway.py - message first occurred at 10:04:44 AM and shows up 3 times
Couldn't start deCONZ = dresden elektronik deCONZ protocol: ConBee I/II, RaspBee I/II coordinator (attempt 1 of 3)
10:11:08 AM – (WARNING) Zigbee Home Automation - message first occurred at 10:04:37 AM and shows up 9 times
I tried the suggestion to swap the Conbee’s USB port but no good. Usual restarting of HA, reboot Proxmox, etc, no change.
So I reloaded the USB port pass through setting in Proxmox. I followed this guide:
Once I had done that the ZHA integration reloaded successfully and the Zigbee network is back operating normally. Pool pump is now back on and the outdoor lights are off!
It was a bit of a fluke frankly that I tried that, mainly because I have little clue what I’m doing!