I had the same error message as well. The solution for me was updating the OAuth URI in the EventBrite application details.
In Keyring where you enter the API secret etc, there is a block of text that has the OAuth URI such as
domain.com/wp-admin/tools.php?page=keyring&action=verify&service=eventbrite
Then I went to EventBrite at https://www.eventbrite.com/myaccount/apps/ Clicked on the key details and updated the OAuth Redirect URI field. After attempting to authenticate again I was able to get the Allow/Deny options to show up.
