Hi,
So I don’t know if the problem was fixed or not, but as of Friday, March 29th, 2019, I’ve been having the same issue. I was playing galactic assault when suddenly the game crashed and I haven’t been able to connect since then. “Error code 721.”I checked my router and Xbox and they are working fine, which leads me to believe the problem is on your end. I’ve tried multiple supposed internet fixes, such as going to th collection screen to log on, but so far nothing has worked and I haven’t been able to play for 3 days. I appreciate answers/help. Apparently the servers did crash but people are playing now, so I guess it’s isolated.