google web apps embed pdf credentials fail

I have a google web apps script that delivers a web page and am trying to embed the pdf viewer to display pdf's from google drive, but am failing even with the example code. I have created a credential for the gsuite user running the apps script, and the script works without the embedded viewer.  When i run it with the embedded viewer I get an error message, how can i make this work / get the right credentials?  error message is - File preview not available; This application domain (https://n-w7drqfmvzgqptnxawu3wfueo6gcdcos4n6gmjxy-0lu-script.googleusercontent.com) is not authorized to use the provided PDF Embed API Client ID.