Honeywell T6 Pro WiFi going unavailable in Homekit

Hello,

I have four Honeywell T6 Pro Wifi thermostats and use them with Homekit in HA. Within the last 48 hours, they have started going “unavailable” in the Homekit integration. I also have the Honeywell Lyric integration installed, and they do not go unavailable there, nor do they disconnect from the Resideo app or the wifi. This problem seems to be isolated to Homekit. I prefer using these t-stats with the Homekit integration for local control so I don’t have to deal with Honeywell’s server polling limits.

The only change I’ve made to my home is a recent install of an OPNSense router. Is it possible the new router is messing with homekit traffic? I have UPNP enabled on the new router, and have looked for advice regarding port forwarding, but I can’t find anything specific. I have the router set to assign each thermostat a static IP, but that didn’t fix the problem.

Any advice would be appreciated. I’m tempted to switch these thermostats out for the Z-wave model as I think that would probably be more reliable than Homekit.