Very solid game you have here, I tried the web build and it was working fine for me, only thing that bothered a little was the audio when the points went up, it sounded a little bit rough. But I really liked what you did here with "connections"!
Yo I am so sorry to hear that you had issues with the game. I have tested the game once again and yes you were right I somehow missed the leave button not working. I have fixed the issue now and multiplayer should also work.