Get PowerBIEntityNotFound when trying to do a simple report rebind with rest api

I thought this would be something extremely simple for me to do but I'm getting the error:  

cache-control: no-store, must-revalidate, no-cache
content-type: application/json; charset=utf-8
pragma: no-cache
requestid: 319 


{"error":{"code":"PowerBIEntityNotFound","pbi.error":{"code":"PowerBIEntityNotFound","parameters":{},"details":[],"exceptionCulprit":1}}}

 And I'm not sure why.  

I'm doing this from this link:  Rebind Report Rest API

I have admin abilities on the workspace where the report and semantic model reside.  

I filled in the report id and my body is just 

So what am I missing?