I have Office 365 (hence Excel 2016).

When I click on the icon for Word, Access or Powerpoint the program loads almost immediately.

BUT, when I click on the Excel icon it takes forever (i.e. somewhere like 90 seconds to 2 minutes) for the program to load !

In addition, if I click on an existing Excel file (whether *.xls or *.xlsx) it takes also forever and, at the end, the system tells me there was an error and the program finally appears with a brand new, empty "book", so that I have to enter the file name to have it show in the program. However, if I click on a Word, Access or Powerpoint file name the respective program loads and the file appears.

So this is obviously an Excel problem. What causes it and how do I correct it ?