If you are running into an issue where you are unable to register for a future workshop, you may need to check if you have already attended the same Workshop in a past date. If you did not attend that workshop, but still unable to join the future date, we recommend to reach out to an Administrator on your Learning team who will have to mark you as "Did Not Attend" in the past Workshop.
If your Admin requires guidance to marking a User's Attendance in a past Workshop, refer them to the Article How to Mark a User's Attendance in a Workshop