Im having problems with the Defiant and Noble map packs. When I start a matchmaking search on SQUAD DLC the game finds players but then the search starts over after the map and game type have been picked. Plus after a few times of the game restarting the search I recieve a warnig for quiting to many games and I havent quit a single game today. All other maps work even Anniversary. Just not Noble and Defiant.
Download Reach to your hardrive and see if that works. Thats what helped me out when I had that problem.
Try re-downloading the maps
I tried both redownloading plus installing the game to my hard drive. Also I cant access them from costum games. It says that "Players have failed to load maps. Any information will help.