I had the same issue where HEX Deck would not recognize my server (deck said it was offline) but TrueNas UI worked. I realized it was my fault, I blocked it on my ubiquiti firewall accidentally when i was troubleshooting another issue. That's why truenas works because the HEX OS Deck has to call to Eshtek's server and the truenas ui does not. to answer another question in this forum, the local ui will mask this issue, not fix, because it will allow local connection, but wont change the fact that your server is blocked from external internet firewall level so connected to Eshtek wont work (only for this exact issue though). Another symptom of this exact issue was truenas did not have external internet access either, the app catalog was failing to update. Good luck to you guys hopefully this helps.