Steam HD issues

hello! As nostalgia, a lot of my friends bought the game on steam, and we have been playing sometimes since last July. For the past few weeks we encountered a problem which makes the few times we are able to play impossible. The problem at hand is that we can't join each other's lobby. If for example a 3rd friend sets up a lobby and we manage to connect, we still cant ready up cause we cant connect to each other with some friends. I'll upload an example image. I tried finding a solution, but I couldnt. I know of voobly, we want to play on Steam. Like we used to. We all have high-end internet connection, so that shouldnt be the problem as well. Same version also. Thanks in advance! The picture: https://imgur.com/a/4yd0J