Had the same issue this week:
grid suddenly offline, after about an hour, the power went back on, HA did not reconnect.
Pulled the NUC, did a fresh install, nothing worked. Finally it seemed that the NUC got another IP adress from the router, and the port forwarding wasn’t set for that IP adress!!!
Check your router first if you get a situation like this!
I have had running on a pi 3. Aftersome time, I can’t connect to ha (it’s connected via WiFi). That’s using an Ipad via the IP/port 8123.
I get can’t connect every time.
But if I tryfrom my windows 11 pc using the same IP/port it connects fine. All devices connect to same WiFi.
Mac user here. I had a similar issue. With the new Sequoia release, there are more granular permissions should be granted to apps. Turned out to be browser related. Even through I granted Chrome the access to find devices on the local network, it just didn’t succeed. I had to switch to Safari, which worked fine for the homeassistant.local:8123 address. Just sharing my experience as might be useful for someone else.