REST API - Tables load in Transform page but Apply Changes fails

I have successfully created data sources driven from the REST API for Reports and Pages. For now I'm just getting the hourly token from MS and inserting that into the Query.

I was then able to paramterize the ID of the report and using that to retrieve all pages for all the reports.

These load just fine in the Transform Data page, but when closing the window and applying changed, PBi fails:

Failed to save modifications to the server. Error returned: 'OLE DB or ODBC error: [DataSource.Error] Web.Contents failed to get contents from 'https://api.powerbi.com/v1.0/myorg/reports/{a GUID is here}/pages' (400): Bad Request.'.

The token is fresh.

Any ideas about what could be happening?