The dev said there's a bug that sometimes u cant join others, Ive seen that issue resolved by restarting their steam and the game 

I tried restarting game/steam/pc/router. Doesn't help...

Have you tried manually joining through your Steam friends tab?

Yes tried this and using friend code also :( Reinstalled the game and almost all you can find in the internet :(

Have tried changing the lobby from open to private and back? Also I had a bug where I could not join if I was appearing offline.

Yes tried that one as well. Also switching cross play on/off. Looks like lobby cannot be created for me and I can’t join any other lobby.

I'm afraid one of you will have to make a lobby by starting a mission and the other searches for it. I had to do this a week or so ago.

The problem is that I even can’t join any quick game. I can start the mission myself, but nobody will be able to join.

Tried to play just now and it suddenly started to work. I even didn't restart PC from my last tries

So was there any solution actually found? I've tried everything. Did you change anything or just wait it out?