I ran into this problem sometime last year and now it’s back again! I can’t seem to find a match in free-for-all at all and my search preference is expanded! I don’t know what went wrong but something they did with one of the updates messed up this playlist. Surely it can’t be because nobody’s playing it. That to me doesn’t make any sense. 343 please fix this!!! This is my most played game type and now it’s not working! Please Everyone! let 343 industries know about this problem!
Try a hard reset of your Xbox. I use a balanced search and never have an issue finding a game in FFA.
Its likely because of the population at your ranking. After all the randomness of it is pretty rage inducing. My best advice is to search on expanded. I often have to wait long periods of time to find a FFA match too.
I have the same issue since I came back to the game in 11/2016. A hard reset or altering the matchmaking criteria did not work.