Can't Join Multiplayer Games

[Perzival12]

Hey, so lately I've been trying to join some online games, but everytime I try, I get this error: 

                        Failed to connect to server

          This is often caused by UDP port 20595 not being 
     forwarded on the host side, by a firewall, or anti-virus 
                                     software.

I made sure I only have the compatible mods on, and I tried joining a bunch of different games, but I always get the same error. Is it because I am using a FlatPak? Or is it some setting on my computer? I am using a Librem 14 with PureOS installed, if that is important.

[Vantha]

https://gitea.wildfiregames.com/0ad/0ad/wiki/FAQ#what-shall-i-do-when-joining-multiplayer-matches-fails-with-an-error-message

By the way, in the future (starting with R28) there will be a button on the error dialog that opens this FAQ entry directly.

[Perzival12]

5 minutes ago, Vantha said:

https://gitea.wildfiregames.com/0ad/0ad/wiki/FAQ#what-shall-i-do-when-joining-multiplayer-matches-fails-with-an-error-message

Thanks.