There are a few reasons why you as the admin would want to block a participant's access to EnagagementHQ. Arguably, most likely because a user has repeatedly breached your site's rule and has therefore lost their rights to continue using your site.
As a site admin you can at any time block and unblock participants. This can be done by clicking on the Participant link in the side navigation bar and then clicking on the Block option in the Participant page.
Being blocked results in the participant not being able to make any submissions where verified participation is required or access protected projects they had been granted access to. In addition, it will remove them from the mailing list of your EnagagementHQ site and they would no longer receive any newsletter you sent to your database from within EnagagementHQ.
It should be noted that project admins CANNOT block participants. Only site admins and hub admins can block participants. In addition, participants are not automatically notified about their status. If you want to let the user know that their access has been revoked, you may do so by sending them an email.
Note: In EnagagementHQ you cannot delete participants completely. Read the article Can I permanently delete a participant? to understand this better.
Contact our support team if you need any further assistance via chat or email firstname.lastname@example.org