App Login Proxy "Unable to generate token for this server"

AndrewPage1

I am attempting to implement the Proxy for App Login detailed in the following:

ArcGIS Security and Authentication | ArcGIS for Developers 

However, I am getting the error below when the proxy code is attempting to convert the token 'from a Portal token into a Server token':

{"error":{"code":400,"message":"Unable to generate token","details":["Unable to generate token for this server"]}}

The code is doing a GET to the following URI:

https://www.arcgis.com/sharing/generateToken?token=<token>&serverURL=https://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer?f=json&f=json

Is there any reason why a token would not be able to be generated for https://services.arcgisonline.com?

rgomes

This URL have a TOKEN parameter. How you are getting the Token to use with this request?
Did you follow the steps just like the link below:
ArcGIS REST API