Workbook Performance sidebar suddenly not working

Hello, I'm having a really strange problem that neither Google nor LLMs seem to be able to solve.

When I press Check Performance in the Review tab, the Workbook Performance sidebar opens, but it's completely blank/empty.

I have tried a bunch of different solutions suggested by Gemini, including a full online repair, which removed and reinstalled Office from scratch, but the issue persists.

Anyone encountered this problem before and know of a solution?