This looks more like a security issue for the user that tries to import the document. Does the user has the needed security role to import?
Regards,
Ronald
[EDIT]
See documentation here: https://world.mendix.com/display/refguide5/User+Roles. The Excel importer has module roles. The user that needs to do the import must have the module role assigned to this microflow which is configurator. So make sure that the user has the module role configurator otherwise you get the error.