Graphs on excel

debraonsurez  The following cause seems unlikely, but just in case... 

Right-click the tab on the worksheet that contains your graph.  A context menu (popup menu) should appear.  Is there a menu item on it labelled "Unprotect Sheet..."?  If so, the worksheet is protected (some or all changes and capabilities are disallowed), and that protection is very likely the cause.  Click the "Unprotect Sheet..." menu item; either that will unprotect the worksheet, or it will prompt you for a password (the password that was used when the worksheet was made protected).

If instead the context menu contains a menu item labelled "Protect Sheet...", the worksheet is unprotected, so... ???  When you (left-)click on a graph, do selection handles (small circles at the corners and on the sides of the graph) appear?  And which version of Excel are you using?