Whenever any customer books appointment in your store, the customer will receive two email notifications:
One email from Shopify with order details, confirming the purchase.
Another email from Servv server including the appointment details and the Zoom link to the event.
However, following are the prerequisites for Email notification service:
Zoom does not allow event/appointments bookings (registrations) for Free Zoom accounts. You must connect your PAID Zoom account to allow event/appointments bookings and email notifications.
You can refer to the Zoom article - https://support.zoom.us/hc/en-us/articles/211579443-Setting-up-registration-for-a-meeting for more information.
Check if "Registration" is enabled in your Zoom account. To enable registration follow the steps below:
Login to your Zoom account. Go to Meetings, and from the list of meetings, select the option “Edit”.
There you need to turn on the registration and save the changes. This will be applied to all the meetings that you will create further.
3. Also, make sure that the customer can only check out using email. Follow the steps below to enable this action.
First, go to your store settings > Checkout.
Next, go to "Customer contact" section and select the option "customers can only check out using email".
Now the registrants will receive the confirmation email once they book an appointment.
NOTE: Sometimes the emails may end up in the SPAM folder for few people. Make sure you ask them to check their SPAM folder if they did not receive it in their inbox.
Refer to this article for more information on email notifications:
How do I use the reminder email feature?