I could be wrong, but I believe the way the email notifications system works is that it doesn't send you an instant email when one of the listed things below happens. Instead, it waits just in case additional notifications pop up and then compiles them all together into a single email.
And if you view the notifications early on the site and clear them before the email is sent, you won't get the email, as the system believes you've already seen the notifcation and has no need to email you.
So waiting on the emails to process all your purchases may be a touch unreliable due to that.
If you wish to keep on top of, and properly process all the payments coming in, I would advise doing so through the payments screen: https://itch.io/dashboard/purchases
Since this gives you detailed information on all of the payments coming, from who, and when.