Trigger Instant Subscription in Power BI

I am attempting to make a web call to trigger a Instant Subscription to email out a report.

I am able to successfully get a Micosoft Auth token via C# and generate the necessary payload below

I am calling wabi-us-north-central-redirect.analysis.windows.net/metadata/emailsubscriptions/instant and delivering the payload.

However I am getting an Unauthorized (401) error. I have mimic all of the headers except the referrerURL. Has anyone had success in this?  The goal is to send the report when the data is ready in the on prem server.  I will kick off a data refresh and send the instat report.