Hi Cutaway2019,
it happens sometimes. I would recommend to wait until it gets resolved, don't sacrifice your progress for those few hours. Although most probably you will need to repeat the mission.
I got it as well today right after Survival game, but I was able to continue after 2 hours. Didn't want to sacrifice the progress.
For this kind of games sometimes happens that servers in the background do not scale as they should, following increased data traffic, and then various problems occur.
Hope it helps,
Kold