Spring RTS Engine

I have a problem with connecting to my friend. It just sits at the connecting screen for like 20 secs then exits.
I don't really know what the problem is, I could connect to him yesterday, but not a few days before and not today. Nothing of my computer or internet/routers changed within the time of playing with him yesterday to today.
I have tried with the windows firewalls off and on, allowed the lobby and "spring" in the program files, went into the advanced firewall settings and added things to fully allow the lobby and spring.
Yet I still can't connect after doing anything.
He has ports forwarded for the game.
I'v also tried right clicking the spring files, going to security, and checking everything there in the "edit" thing.

Try to use a "relay". It'll fix your connection problems.

When hosting a game with springlobby there is a checkbox you can enable (see screenshot). It'll add a (not playing) relay-bot to your game (see screenshot).

Using a relay enables chat between players in the lobby and in the game, aswell as late-joining for spec or re-joining in case of crash etc, very useful.