I had a fight with my system when trying to to a OwnCloud setup.
It was constantly saying (after a long wait when trying to open the admin page)
isWebDAVWorking: NO - Reason: [CURL] Error while making request: Connection timed out after 10001 milliseconds (error code: 28) (Sabre_DAV_Exception)
After figuring out the proper URL (https://owncloud.installation.domain/remote.php/webdav/) it dawned to me that the server me not be able to reach itself.
Indeed, adding an entry in /etc/hosts/ to assure that the domain points to 127.0.0.1 instead of the real IP address worked.