I am sure I have included it correctly in my program, also User Management API and I/O Management API is enabled under Services tab in my Adobe Console Integration, of which credentials are being used.
@jayg26932123 issue is related to payload data where you have incorrect url of metascope. Please check the jwt tab in the Adobe IO integration , you will get the correct url required for the payload. I faced the similar issue and after taking the metscope mentioned in the integration, it worked for me. I got the access token using python programming.