I've suddenly begun getting an error message when trying to export a Quickboos report to excel. This has never happened before. The specific error message is "Excel could not open the data file". I tried activating excel as others suggested, but it is already activated.
It seems like the excel does not support the formatting of the Quickbook, Go back to Quickbook and when trying to export the data to excel, uncheck the format options in the export popup window and try again.