If you are getting the "Insufficient Privileges" message on the Mass File Download App tabs that means the necessary permissions are missing,
Here you have to assign the "Mass File Download(Admin)" or Mass File Download(Non-Admin) Permissions set to the user.
Follow the below steps to assign the permission set:
1. Go to Setup
2. In the quick find box type "Permission set" and click on the Permission Sets.
3. Search for Mass File Download Permissions (Admin) or Mass File Download Permissions (Non-Admin) as per your business needs and open the permission set.
4. Click on "Manage Assignments".
5. Click on "Add Assignments".
6. Select users that have the "Mass File Download" license assigned, then click on the "Assign" button.
7. Permission set has been assigned now click on Done Button.
