I'm also having the same issue. I just finished setting up the server yesterday, and I can only access the TrueNAS web interface, not HexOS Deck at all.
When I go to deck.hexos.com and login, then login, it tells me my account was was upgraded to the HexOS Local platform (even though I never opted in), then it redirects me to sign in again, then it never finds the server even when I manually put in the local IP address.