SOLVED: Android TV not connecting to Jellyfin

[skro]

Hello,

I have an issue on my Android TV app which doesn't connect to my new Jellyfin instance.

My setup:
- "old" Jellyfin instance: hard installed on a Ubuntu Server v22.04, version 10.10.3, connected to the app without issue since 1 year (and still works to this day)
- "new" Jellyfin instance: docker installed on another machine, version 10.10.3
- Android TV app v 0.16.6, installed on a Freebox Pop player (an Android TV box from my Internet provider)
Everything is on the same network

The app auto-detects both servers, and displays their IP properly.
It gives me the selection of accounts to choose from, but when I select one, I get the error message "cannot connect to server".

In the server log, I only see these lines upon each connection attemps:

Code:

[2025-08-31 14:11:04.648 +00:00] [INF] [81] Jellyfin.Server.Implementations.Users.UserManager: Authentication request for "enfants" has succeeded.
[2025-08-31 14:11:04.648 +00:00] [INF] [81] Emby.Server.Implementations.Session.SessionManager: Current/Max sessions for user "enfants": 1/0
[2025-08-31 14:11:04.648 +00:00] [INF] [81] Emby.Server.Implementations.Session.SessionManager: Logging out access token "89255ae4c20e46e792ad14c2eaccfda0"
[2025-08-31 14:11:04.654 +00:00] [INF] [81] Emby.Server.Implementations.Session.SessionManager: Creating new access token for user 2f403acc-7f72-4e48-84e0-54d5c17d7514

Network server configuration is identical between the two machines - no HTTPS, allow remote connections.
The "new" server works flawlessly on every other device (iOS app on iphone, Android app on tablet, Windows app and web interface on a PC)

[skro]

I managed to fix it by the following:
- download and install Dune (a fork of Jellyfin for Android TV)
- setup my new server on Dune (as a test)
[it worked]
- uninstall my old Jellyfin app
- install the latest version of the app (v0.18.11)
- setup the new server connection on the Jellyfin app

This time, the connection passed.

I didn't try to reinstall the old machine (as it's due to be decommissioned), so I can't tell if the issue comes from having two servers from the same home network or an outdated version of the app.