stuartbarry wrote: I mean that it should always be sent. But if I click on the email to go to the 'accept' page the email notification goes at once. If I go to the back end, open the event record and click on the accept box the email notification is not sent.

Ok!

So, for now (and it's an known issue today) you will have to approve only on frontend...
The reason i don't have yet add this to admin, is that the process is not the same, and in admin, you can manage appove yes or no (which is not the case in frontend, and for this reason (only possible to approve) it was really easier to add a simple task to process this email notification).

The primary goal of this approval system was to allow a quick link in a email to manager (admin..) of events, to able the manager to click on the link, and then approve directly the event after an autologin to the frontend, and control of user rights and permissions.
This system is not possible in admin as it is today for frontend, as Joomla admin does not work the same way (issue possible with autologin, and managing the send or not of the email notification...).

But, my goal is to change this system, and in fact to improve it in 3.7.0 (the goal will be to have a status system (pending, approved, not-approved, cancel...) with the possibility to integrate the payment plugin i'm working on this Summer, and which one will be first implemented for Registrations.
And in admin, it will be maybe an option button to select if you want to send a notification or not of the modified status of the event.

So, there's a need for improvement here, but i don't have yet enough work on it to give you an clear explanation of what i will do

For the months to come, the only way will be using the link in the email to approve the event.

Hope this helps ?

Best Regards,
Cyril