Excel Custom Cell Formats - Delete button missing

[queenmargot]

Hello! I am trying to delete a custom cell format in Excel. I've done this a zillion times before, but now my "Delete" button is gone! The other spreadsheets I'm working in have the "Delete" button, no problem! How can I get it back? As some background, a lot of spreadsheets in our company are copied from previous ones, and they are carrying over a bad cell format that needs to be deleted. I've done this in a few already, but this spreadsheet that I was given today has the Delete button gone.

Thank you!

 

[queenmargot]

Oh, and the spreadsheet WAS locked previously, but I disabled that.

 

[queenmargot]

All fixed! I had to open and repair, then save as slk, and that fixed it.