Update: A new patch has been released that fixed this issue. If the download doesn't show up, a simple Steam Client restart should do.
Hello there, Metalheads.
We are aware of an issue that will cause the PvP queue to say you must wait 12 hours to play after you finish a match.
This is a bug, a simple restart of the game should fix it for now.
We are developing a fix for it as we speak and plan to have it live in a few hours. Thank you for staying with us :)