Attempt was made by reselling a cert offer

On a cert sale, there is no way to change the offer to 0

If for some reason, you could no longer sell the cert and wanted to stop a reseller from selling it, it's not possible.

Removing affiliate from "manage affiliates" list, does not stop an active resale

Changing the original offer to private only delists the original offer, not the latter.

There should be a way for the original merchant to stop the reseller from selling.