[Win10/Steam] Cannot invite friends to multiplayer

[Sildadia]

Symptoms:
Join game option does not work
Friend can invite me to a game and I get the server ID prompt
When hosting a game, cannot hover to view server ID
Persistent on EU4 and Stellaris (presuming all Paradox titles)
Can successfully invite to non-paradox games (7 Days to Die used as test case)

Things I've tried:
Delete EU4 folder
Verify game integrity on Steam (steam found no issues, did not attempt to download files)
Uninstalled EU4 via steam interface. Uninstall successful
Reinstalled EU4 via steam interface. Problem persists.
Verified no mod conflicts (all mods disabled or unsubscribed for all of us)
Verified we are on the same patch (1.29.2.0 manchu)


Windows is up to date, steam is on current client version for all of us.

I'm out of ideas... thoughts?

 

[AndrewT]

In Stellaris, both you and your friends opt into the "stellaris_test" version in the Steam Betas tab for that game. That uses Paradox MP instead of Steam. If that works, you almost certainly have some ports blocked by firewalls that Steam needs:
https://support.steampowered.com/kb_article.php?ref=8571-GLVN-8711