Power BI Report Server dataset API presents data as JSON - Power Pivot expects XML - how do I fix?

We're working with an on-premises Power BI Report Server and I have a cached dataset.  I want to make this available to Power Pivot users but it is expecting an XML structure.  When I enter the URL for the data feed (http://<reportserver>/Reports/api/v2.0/datasets(<ID>)/data), I get this error: Cannot connect to the specified feed.  Verify the connection and try again.  Reason: Data at the root level is invalid.  Line 1, position 1.

When I put the URL into a browser, I get the data in a JSON format.  When I use Power Query, I can see the data.  When I use Power BI Desktop, I can see the data.  Can someone help explain what I need to do in order to get this data to be made available for Power Pivot?  I'm using Excel 2016 in case that's important.