When I send the enroll invitation email to the user I got issue please refer the [Image1 & Image1] screen shot for your reference.
And also please find the below linkView the doc which I have referred to setup Email configuration in EMM.
Version I have tested in 2.1.1 and 2.2.0 Beta
This issue is probably due to misconfiguration of email template configuration located at "/repository/resources/email-templates" directory. It looks like you have accidentally changed the xml element.
Thanks,