I followed this article to build a SharePoint document viewerhttp://groupdocs.com/docs/display/viewernet/How+to+Build+a+SharePoint+Document+Viewer+Using+GroupDocs.Viewer+for+.NET
The main document can be viewed on the viewer. However, the thumbnails cannot be displayed (please see the attached file 01.png)
I tried to copy a thumbnail URL and paste it on browser. The browser shows 403 FORBIDDEN (please see the attached file 02.png)
I'm using the GroupDocs.Viewer v2.10.0
Any help will be appreciated?