I have both a Nabu Casa cloud subscription and a local VPN. I am unable to launch Home Assistant UI vi either method remotely. However, I can VPN to my home network, ping the NUC/server, and even hit the observer URL with no issues:
Supervisor: Connected
Support: Supported
Health: Healthy
I am physically not at the location so I can't do a hard restart (e.g. pull the power). Any other options?