Default Notifications Settings not Saving

I am trying to change the notifications template but after each time I save it, it reverts back to the default settings. I tried changing the “On Pending” notifications.

I wanted to replace “Dear %customer_first_name% %customer_last_name%,
The %service_name% appointment is scheduled and it’s waiting for a confirmation.
Thank you for choosing us,
%company_name%” with something different.

After 5 times, it still won’t save my changes.