Problem

After upgrading to Confluence 5.7.x, user is unable to preview Office Documents (.docx, .xlsx, .pptx) attached in the page.

Diagnosis

Environment

• Confluence is running behind NGINX Proxy

Diagnostic Steps

• Try attaching new Office Documents file and preview it. This should work, otherwise this article may not be applicable.
• Try to preview the Office Documents in all browser to see if it's browser related issue.
• Compare the properties of problematic attachment and working attachment. If the properties are different, then this article may not be applicable.

Cause

The new File Previewer is will be looking for content cache to display the Office Documents. In this case, NGINX Proxy doesn't allow caching.

Resolution

Add the following configuration in NGINX cache configuration:

...
       set $do_not_cache        0;
       if ($request_uri ~* ^(/secure/admin|/plugins|/rest).*) {
                set $do_not_cache       1;
       }
       proxy_cache_bypass       $do_not_cache;
...