It's happening to XBox players as well. Someone there got a hold of the customer support and customer support acknowledged that a lot of people are having the same problem and they are working to fix the issue. I'm having the same problem. I had to reinstall the game so I could drop the mission and do other things, however…
I'm on PS4 and had the same issue and it looks like everyone else has had the same issue at the same time. So it's a new problem I take it. I reinstalled the game so I could go and do other things. However, I'm not getting any new missions. I'm having to do patrols and such for experience.