If USA Gymnastics adds a level to your sanction after you built the meet in MeetMaker, that level does not exist on your event and clubs with athletes in it cannot complete their registration.

The club sees a message naming the level and is told not to change their roster. MeetMaker support is emailed at the same time and will contact you.

The fix is yours: open the event in the Event Wizard, add the missing level with its fee, and save. Then tell the affected clubs they can process their alert again.