This has to do with an issue of transferring your already completed assignment in the SSA course on the old Pega Academy website. Unfortunately, they had to make a decision when porting the course over and it affected some of the students like yourself. You should still be able to go through and complete the modules, quizzes, and challenged without issues. Sorry for the confusion.
We did not face this issue with the Business Architect or System Architect courses as these were new on the new release of Pega Academy.