A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
First check: have you got more than one sheet selected?
Right-click on your chartsheet's tab and if Ungroup Sheets is an option at the bottom of the pop up menu, click it.
Cheers
Rich
PS. Second check: if you create a new workbook, throw some data together and plot a chart, do you still have the same problem?