Spreadsheet won't let me merge cells

[Mark Jarrett]

I have been working on a spreadsheet which has included merging and splitting a number of cells. However, the 'Merge & Centre' icon in the toolbar has now 'greyed out' and won't let me carry out these actions on this spreadsheet any more.
It does though work perfectly fine on other spreadsheets.
Any idea why this functionality has deactivated on this particular spreadsheet ?

 

[RichardMGreen]

Check to see if the worksheet or workbook is protected.

 

[Mark Jarrett]

'Protect Sheet' and 'Protect Workbook' are two additional functions that are also greyed out.

I think though I have just cracked it. The 'Shared Workbook' editting box was ticked. Unticking this seems to have resolved the issue. Life is all rosy again. Many thanks.