ISSUE:
Document preview for SharePoint 2013 search results randomly give an error "To start seeing previews, please log on by opening the document".
CAUSE:
The behavior occurs because the page that we use to show the preview (_layouts/15/wopiframe.aspx) is set up for anonymous access. Since the user did not browse the site collections from where the documents to be displayed reside, there is no access token which can be presented in order to retrieve the file. If the browser does not supply the authentication token with the request for the page, the user will be authenticated anonymously, which will not have access to the document that is supposed to be shown in the preview. Now in the case where the user is authenticated, the browser sometimes drops the authentication token so that even though the user is authenticated on the outer page, the wopiframe request does not contain the auth token and we end up with the “to start seeing previews…” message.
RESOLUTION:
For Windows NTLM authentication only, a fix to target this scenario is included May 2014 CU or later.
For other authentication providers including Kerberos, there are a few workarounds:
1. Use the Wopiframe2.aspx logic in place of Wopiframe.aspx:
1. Open the file location C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS
2. Locate wopiframe.aspx. Rename it to wopiframe.aspx.bak. – This will be our backup copy.
3. Locate Wopiframe2.aspx. Make a copy of it and paste it in the same directory. Rename it to Wopiframe.aspx.
4. Open the file location: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\TEMPLATE\LAYOUTS
5. Repeat steps 2 and 3 within the 15\Template\Layouts folder.
6. Reset IIS on the box.
– Possible issues with the above workaround:
-Anonymous users may get prompted when looking at document previews.
-Wopiframe.aspx could be overwritten and set back to default by a CU.
–Previews of Excel files may return message "We can't show a preview of this item".
2. Switch to NTLM
3. Disable the preview functionality
4. Refresh the browser
