I came across this issue where I did a magical stuff with my Excel and the Graphs in PowerPivot wont open up in Power BI when I ask a natural language question from Power BI.
So I decided to investigate. I was receiving error message that Microsoft Silverlight needs to be installed. I have installed an updated version of Silverlight in my machine so whats the problem?
Apparently Silverlight is not supported by Chrome in Versions 42 or above.This issue occurs because these versions of Chrome block Netscape Plugin API (NPAPI) plugins from being displayed in the browser. Silverlight is an NPAPI plugin. (Reference: https://support.microsoft.com/en-us/kb/3058254 )
So there is a workaround that you manually Enable the NPAPI plug ins and it will work fine then.