Error during ION API call


we have a requirement to stitch multiple documents in Infor Document Management.

we tried calling the IDM API,

GET /templates/assemble, which gives PDF as output.

This API works well when calling from IDM's Rest API invocation screen.

This API fails when invoked from the IONAPI screen, with "Unauthorized" error. attaching the screenshot of the errors.

ION API Call Error.docx

any suggestions?