Option on the portal "Compare to original" gray out

Hi MDM Experts

I just tried to use option on the portal "Compare to original" meaning is to compare check out records.

That option is gray out, and I do not know how to work with that step:

The portal user is a member of the MDM check out group

from documentation:

http://help.sap.com/saphelp_mdm550/helpdata/en/45/c7af7a39ee570ae10000000a114a6b/content.htm

I check there is not such group on the Portal. My user is Admin in MDM console.

Can you help me which permissions should I grand to be able to compare records on the portal?

Thank you.

BR

Rafal