I am working an Excel workbook and I am trying to Share the book so that one
or more users can edit at once but the option to do so is greyed out.

I have unprotected the workbook and this does not solve the issue. I have a
few macros in the book but this has not stopped me sharing in the past so I
can see no reason why I would not be able to share the workbook.

Your help would be much appreciated