How to add buttons in context menu in a Doc Library which is added as a WebPart inside a SP page

Hi, 

I created list view command set extension application for adding a custom button into the context menu.
I have a SharePoint Page in which I added a document library as a webpart.
In the Serve.Json of my application I have given this page URL to apply the custom button into the library.
Around 2 weeks back this approach worked and the buttons were shown in the context menu but now they are not showing. 
In a normal document library it is working and showing the Custom button. but in a page where a document library is added as a web part it is not showing. How can we achieve this?

What could be the Reason? And Please give me any solution to achieve this functionality. 

Note: I have tried this solution with different SharePoint Sites but it didn't worked.

Thanks in Advance