SharePoint 2013 – Error while creating a new site collection “User cannot be found”.
SharePoint 2013 – Error while creating a new site collection “User cannot be found”.
Issue: Error while creating a new site collection “User cannot be found”
Description: Was able to create a new site collection on another farm using the same account. Also was able to create a new site collection on a new test web application on the problem server with this user account.
Solution: Turns out the issue was due to enabling Trusted Identity Provider (STS) for Forms login for external users on site. For some reason, after enabling STS, SharePoint was failing to identify Windows NT ID.
Once the STS is turned off, you can create the Site collections.
Click on top of WebAPP -> click on Authentication Providers -> click Default -> uncheck Trusted Identity Provider
See more at: http://expertsharepoint.blogspot.de/2014/08/sharepoint-2013-error-while-creating.html
Note: Resolved the issue by above method. If you find a different solution, please report it as a comment to this post. This will be useful to SharePoint Community. Be sure to double-verify it: undo your solution and verify that the problem comes back, then redo it and verify that the problem goes away.