Stranded FBA Inventory: Missing SKU, Can't relist "No record of SKU"

I have 21 units of stranded inventory under an ASIN of mine, for a product I’ve made. The category was changed for this listing, and it was removed from the variation family it used to be in. I seem to have broken this SKU by using inventory file uploads, leaving it stranded. I tried to add it as a child to the original parent, and I tried changing its category. Eventually, the inventory was stranded.

When I try to relist the inventory, I get

" * Sorry, the SKU you have provided doesn’t match any of our records."

When I try making a new listing under that ASIN, I can - No problem there. When I try to bring back my stranded inventory by entering the stranded SKU, I get the error in the image included: “You are trying to contribute details which may not be allowed, check Amazon’s Generic policy”

Selling partner support is of no help, telling me to “Delete and relist the ASIN” or to “Make a new offer with the same SKU” or to “Make a new listing” but the same error comes back every time. Jeff@amazon.com simply redirects me to selling partner support, which copy-pastes the instructions for making a new offer back to me. My inventory has been stranded over a month now.

Has anyone faced this before? I would really appreciate the help.