When we see a 5566 error in the InfoPath form loading with a correlation ID and we see (401) Unauthorized error in the SharePoint ULS logs, we will have to check the below mentioned settings on an On-Prem SharePoint farm
- Disable loop-back check and make registry changes as per the article http://support.microsoft.com/kb/896861
- Check if the 127.0.0.1 mapped to the web application Fully Qualified Domain Name in the hosts file.
- Make sure on Network Load Balancer, persistent cookies are enabled and have a good amount of time out value set http://technet.microsoft.com/en-us/library/jj573814(v=office.14).aspx .
- Check InfoPath form security and trust setting, provide full trust and publish the form.
- If SharePoint is using Claims based authentication and if the it is SharePoint 2013 by default claims based authentication is enabled, follow the article to set up the data connection : http://blogs.technet.com/b/rajbugga/archive/2013/08/07/infopath-over-claims-authentication-sharepoint-2010-amp-2013.aspx ( if you ask why we use udcx format data connection for Claims based authentication sites --> http://msdn.microsoft.com/en-us/library/ms771995(v=office.14).aspx and http://blogs.msdn.com/b/infopath/archive/2006/10/02/data-connections-in-browser-forms.aspx)
- Increase the data adapter time out value form the Central Administration site and test the behavior.
- Check the proxy settings on local machine and the web application web.config file (refer : http://blogs.technet.com/b/jasbro/archive/2008/02/05/eventid-5566-troubleshooting-in-infopath-form-services.aspx)
- Try using central admin URL and pull the SOAP web service.
- Make sure the SharePoint Enterprise features for browser based forms is activated.
- Check the time out settings on IIS and Network Load Balance (F5, netscalar etc.)
Published by: Menaka Sarkar B.