Adobe sign API Ajax call

Trying to do a simple ajax GET request. Tested via a web page with the exact same credentials and it works first time as can be seen in the first image.

Trying to do manually with an Ajax call in code and I am getting no where, no response at all.

The preflight OPTIONS request returns 200. But the GET request doesn't return anything, no error message nothing. Really frustrating.

Any help/advice would be appreciated.