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.
I have a Scout that I’m not able to enter Advancement in for because I keep getting this error but she is absolutely in the correct den.
Youth is not eligible to earn this advancement and must be registered in the appropriate den level for this rank. Please click here to return to roster and assign to appropriate den.
It’s extremely frustrating just like everything to do with the new updates.
Actually, your question prompted me to go back in with a different angle, and I created a new arrow of light den and moved all the kids and deleted their old den and it seems to have fixed the problem.