My customer had a requirement to download the Summary data of the report visual for Power BI embedded report.

I went to achieve this as a wrong path first. I hope you don’t do the same mistake.

The path I first took was to use the REST API below.
Datasets – Get Dataset -> https://docs.microsoft.com/en-us/rest/api/power-bi/datasets/getdataset

Push Datasets – Datasets GetTables -> https://docs.microsoft.com/en-us/rest/api/power-bi/pushdatasets/datasets_gettables

DO NOT use those APIs to get the dataset of an existing report. This will not work. These APIs only work for the data you pushed via API. The data set will show the API ACCESS as shown below.

To download embedded report data use the Power BI client JS api to download.

Export Data-> https://github.com/microsoft/PowerBI-JavaScript/wiki/Export-Data