Adobe Sign for Salesforce, no permission to execute the operation error when uploading signed PDF

Hi,

I had this access denied error (no permission to execute the operation) when uploading a signed PDF through the salesforce Adobe Sign app in our Salesforce org.

and please see attached the screnshot, I managed to find out there was the API callout to adobe Sign when I was uploading the file, can anyone please help me what could be wrong with this signing tokens step,why I am getting 403 error?

Many thanks,

Jun Liu