Go to your 'my ebay' Scroll down til you see 'My Account' on the left Click on 'Preferences' All 3rd party authorizations you have enabled are there, near the bottom of that page
Then it sounds like you have no 3rd party authorizations (did you get a confirmation from Auctiva?) The only place you'll see it on Ebay is in preferences.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .