You can unblock the referrals from the Referrals tab in the CSP:
Keep in mind that not every blocked referral can be manually unblocked; it can only be unblocked if it was blocked due to the fraud settings. For example, if it was blocked because it didn't suffice trigger criteria in the campaign (i.e. the Friend's purchase wasn't large enough to fit the minimum purchase requirements), you will not be able to unblock it and send the Advocate their reward.