The most common reason why E-mail notifications would not go out is because the notification settings are turned off at the time of raising the invoices.
To verify if that is indeed the case, please go to Income->Invoices — Click on “Billed Invoice Groups” button.
You can see list of all Invoice Groups that been created. Filter on the one that you have raised – in the Actions column click on “Modify Details” icon (highlighted in screenshot below)
In the resulting pop up, you can see towards the end if Email and SMS notifications were turned on or off for the invoice group when you have raised it (screen shot below).
If the check-boxes are not in selected state, this means the notifications were turned off and hence no emails / SMS went out. If you want to send the notifications now, please check these boxes and update the invoice group. Once updated, click on the “Re-send Invoices via E-mail and SMS” icon in the actions column. This will schedule the invoices to be notified via email (and SMS if the check box is checked) with in next 15 minutes.
If you see that the check boxes are checked and its more than 30 minutes you have raised invoices and do not see any email notifications, then go to Reports->Email Delivery Reports from the left side menu. Select the date on which the mails were supposed to go out (when you have raised the invoice) and click on the Show Email Delivery Report. That shall show the list of mails sent out for invoice. If you find some emails, it means that the emails are still getting sent. If this list is empty, you can check back after an hour or so to see if all mails have gone out. If there is no change here even after waiting, please write to support with the invoice details so that they can assist you with a resolution.