Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
Is it just a particular merit badge, or is it all merit badges you’ve tried? This is usually because the scout has a hanging membership in a pack in Scoutbook.
If you or a unit admin goes to the scout’s Memberships page in Scoutbook, you can put an end date on the pack membership. If that’s not the issue