Error Message While Starting

I have been receiving an error message while trying to play Forza Motorsport 6 and Forza Horizon 2 that reads, “An unknown error has occurred. Please try again later.” I called Xbox Support and we tried many different things, but none of them worked. They told me to contact the developer of the game(s). Forza Motorsport 6 is probably my favorite game on my Xbox, and none of my other games are doing this. I don’t know if anyone else has received this message in either game but it won’t let me play at all. Should I uninstall and reinstall the game?
Ben Moore