This is a compatibility issue between eCart 5.0.7 and Universal Email 4, eCart 5.0.7 Does not recognize Universal Email 4.
Universal Email was replaced by Form Builder, and finally by Data Bridge.
When eCart was updated to recognize Data Bridge as the package containing email functionality, it no longer worked with UE 4.
I beleive eCart 5.0.5 worked with UE 4. I can send you a copy of that version via email if you like, or the recommended option would be to upgrade to Data Bridge which includes a New Version of Data Assist