Unprotect Sheet suddenly greyed out

I have protected a worksheet as it has several formulae on that I do not wat anyone else to mistakingly delete. I then have spent time on setting up a sheet to track changes (just in case this has any bearing on the problem). This is the only thing that I think I have changed since protecting this morning and now I cannot unprotect the sheet. I have not protected the workbook and the unprotect sheet function is now greyed out.

Any ideas?

Yes, you cannot unprotect the workbook while it's being shared. Under Tools>Share Workbook, the check box needs to be unchecked. Then you should be able to unprotect your workbook. Did that solve your problem?

ChemistB

Thank-you. I had kept looking at the highlight and track changes method but couldn't see how to turn it off.

Many thanks again!