We have detected an error from the managed system. Error Received: [ConnectorError] Exception occurred while generating access token. when trying to connect web service saas to oracle

I was able to test it successfully when I copied everything from the Postman code snippet. All the header keys, values, urls, etc.

with things like content_type failed and when in Postman it was Content-Type and it worked.

So, I would suggest use everythign as-is from Postman