I've been having this problem for ages and have replotted each plot from scratch as a workaround but enough is enough.
When I copy a plot and paste a plot within the same excel sheet the copied plot is blank apart except for a series point at (0,0). In the 'select data source' window the X axis and Y axis formula links to the sheet via a 'Users/username' string rather than the tab in question. I only have this problem with some spreadsheets. Have I done something in the past to cause this and is there any way to solve the problem?