For Zoom users
If you see a Request pre-approve option when connecting Zoom to Calendly, that means that your Zoom admin must approve Calendly for Zoom before it can be installed. Select request pre-approve to send a request to your Zoom admin. They'll receive a notification from Zoom with the request.
If you are also your Zoom account admin, you can continue to the next step. If you are not a Zoom admin, you will continue to see the request pre-approve option, and will need to contact your Zoom admin to continue.
For Zoom admins
If you're a Zoom admin, you can select pre-approve while connecting Zoom to Calendly or from the App Marketplace, under the Calendly for Zoom app. Once you pre-approve Calendly, all users on your Zoom account can download it. For more details, view Getting Started with the Zoom App Marketplace.
Pre-approve when connecting
Pre-approve from Marketplace