Default Document preview is not working in share point 2016

I am using the search result web part to display the results. But in my case, the document icon is showing but the document preview is not showing. When I further debugged, it clearly shows that the ctx.CurrentItem.ServerRedirectedEmbedURL is null and all other ServerRedirectedPreviewURL and ServerRedirectedURL are also null. I have done full crawl from central admin. Changed the Result type and updated it. Even deleted the display template and uploaded it again. what should I do now?