CDO records upload process - NEXT button not active

Summary:

The NEXT button is not active while processing CDO records upload

Content (please ensure you mask any confidential information):

Have you ever experienced the problem with UI in Eloqua regarding the NEXT button not active while you try to upload excel file with CDO records?
I notice that after creating CDO (saved in system), when I try to upload new records in CDO with "Upload Custom Object Records", the NEXT button is not active. No matter what I do, this is not possible to move forward with the Upload Wizard.
I did try for several test CDOs and this is just not active.