Embed group report problem

I'm trying to integrate PowerBI report (located in group) into my page using iframe

I've registered AD application

I can query list of reports from the server side

But when I'm trying to use received "embedUrl" value using the same token I'm getting following error message:

"This content is not available.
Learn more about Power BI."

At the same time, if I open list of network requests in chrome DevTools, I can see the one request to some page ending in "modelsAndExploration" which return 401 error: Unauthorized

If I'm trying to open URL received in webUrl, I can successfully see report in PowerBI interface

Any suggestions/ideas?