This section will answer the question of how to restart a mission in the Division 2. This will allow you to re-approach the mission if you get stuck or there's an error preventing from completing it. In the guide to the Division 2, you will find a solution to this problem.
There are several ways of solving the problem with the missions. The first option is to change the difficulty level of the missions. Additional difficulty levels are only available when the mission has already been completed, otherwise, only one difficulty level will be available. The photo below shows the map screen where you can change the difficulty level.
Another option is to simply log out and log in again (sometimes it is enough to do it two times). You can also try to fast travel to a checkpoint or settlement (the game will reload when you do that, which might unlock your mission). The last possibility is to try to die - you can commit suicide by throwing a grenade at your own feet. Harsh, I know.