If you're using Blackboard SafeAssignments, it's a good idea to synchronize SafeAssign each semester before assignments are due just to make sure students won't have any problems submitting their assignments.
You can do this by going to:
Control Panel > Course Tools > SafeAssign > SafeAssignments.
In the upper right you'll see the button for "Synchronize this course." Just click that button and your course will be fully synchronized with the Blackboard SafeAssign server.