PowerBI: This content isn't available message

We are using PowerBI embed APIs to generate a embed token & embed url to further render the corresponding report. The report shows up fine on Web & Android, however, iOS devices (iPhone & iPad) fail to render the report showing error - 'This content isn't available'.

The same reports were working on all platforms (Web, Android & iOS) a day back. Furthermore, we entered the code generated Embed Token & Embed URL in the sandbox environment and the report shows up as expected  

Any guidance to debug the issue would be highly appreciated. 

Ref IMGs:

PS - We are using in-app UIWebView.