Hi,

I've seen a few of these reports recently. Just out of curiosity, where are you located? I'm trying to guess what the reason for such sudden problems could be. Anyway from another post, I feel like the issue could lie with relay servers either not functioning properly or them restricting connections somehow. The following is my suggestion from the other post.

If you can, you could try the following (NOTE: This needs to be done for all the players wanting to join the same game and currently only works on Windows).
- Make sure the game is closed
- Navigate to %appdata%/Trine5 and open options.txt on any text editor
- Make sure EOS is disabled. This can be done by adding the following line to the file setOption(networkModule, "UseEOS", false)
- Add the following line to the file as well to disable use of relays when EOS is not in use setOption(networkModule, "DisableSteamRelay", true)
- Save the file and try again

This will disable the use of Steam relays and try direct connection instead, with this option though you might face NAT issues depending on your network setups, but could rule out if the issue is really with relays not working for you for some reason.

EDIT: The DisableSteamRelay should be set to true, had it incorrectly as false first.

- Teemu / Frozenbyte