I started having problems in the past month or so where HomeKit showed everything as ‘no response’. After reading this I started looking into my UniFi home network setup and ended up turning off “Enable multicast enhancement (IGMPv3)” for each wireless network. That fixed the issue immediately and everything seems to be fine.
I’m not sure why it suddenly stopped working when I didn’t change any of my UniFi settings, but I think I remember updating the UniFi Controller software at some point and maybe that’s when it started happening. Anyway, thanks for giving me the idea to look into my router/network setup rather than my HA setup!