Shared Excel file won't Save

Hi I set up a second User account for a friend so an office associate can sign in to access a spreadsheet on his PC.

From the Admin's account I shared to the new account with Read/Write privileges. I didn't see any higher sharing permissions but really didn't poke around much.

So I get a call from him today that associate is able to edit the spreadsheet but not save it to her account, gets an error. I'm waiting for the text of the error to google.

I'm hoping Office experts will know what else needs to be done. Did I miss an extra sharing permission?

The error message in detail will give us more to go with but within Excel itself it is possible to 'protect' the worksheets and/or the workbook. Have you discounted that as being the problem? Cheers.