Make sure in your userlib folder and for each jar you have only the latest version, and delete others if exist.
In the below pic delete the 4.0.0
There is a good chance you will need to clear out the userlib folder and get rid of the libraries that were used by the old version of the Excel Importer.
Unfortunately Mendix does not have any tools keep your userlib clean, so this is a manual job. If you are lucky, the libraries used by Excel Importer come with an additional file “<libraryname>.Excel_xxx.required”. This will help identify which libraries were used by the old Excel Importer and which by the new.