Unblocking someone in Zoom
To unblock someone on Zoom follow these simple steps.
Open the Zoom app on your laptop.
Go to your account in the top right.
Go to Settings -> Chat (on the left sidebar).
Here you have blocked users. ...
Select the user you want to unblock and click Unblock.
After that, you will see that the user is no longer blocked.
If you are the account admin, you can allow rejoining for all members of your organization: