In order to restore correct email templates you will need to do the following:
1. Run the tool attached using Management Shell on any farm server with the following command:
All Email templates will get deleted.
2. Run the following script in Management Shell to recreate Email Templates:
$remUrl = "http://REMaddress/"
[System.Reflection.Assembly]::Load("Elearningforce.Sharepoint.LMS.Enrollment, Version=220.127.116.11, Culture=neutral, PublicKeyToken=a0480eb0bc0ac42a")
$rem = [Elearningforce.Sharepoint.LMS.Enrollment.ObjectFactory]::CreateAddonSite($remUrl)
3. For LMS Suite versions starting from 4.6 some email templates might still be missing in the list. You will need to reactivate ELEARNINGFORCE - REM: Course Material REM site collection feature and ELEARNINGFORCE - REM: Curriculum site feature to recreate them, if these features were activated in REM before.