When queuing for competitive, if it says “game found” or “joining game” for 3 seconds, quit overwatch and relaunch. This has worked for me to get around the “failed to join” error. By the time you get back you should have the option to rejoin the match if it had actually found one, otherwise it will be the normal “play” link but you won’t be suspended.
If you leave it at “joining game” for too long, then it fails, you’ll get the suspension if it actually had 11 other people in a match waiting for you.