Matchmaking is not working! help!

So about 2 days ago I put in Halo 4 like normal and I went to war games. nothing unusual happened, just an ordinary gaming session. So I was waiting for a game of I. Slayer to find players but it wasn’t for some reason. I checked my NAT type and it was Open. The servers weren’t down either. now 2 days later I still have no idea. an error pops up if you wait to long saying “This playlist may not have enough players to successfully start a game” or something along those lines. I just want to play halo and I have looked and looked with no results. so please can someone help!