This message shows when I accidentally close my backup script of the SharePoint site. This massage is prompted by the SharePoint when a site is in a maintenance mode.
- Go to the central administrator
- Application management –> Site Collection Quotas and Locks
- Select the site collection and change the locks information to Not Locked.
Some times this page looks like disabled thus you need to try the method two.
This PowerShell Script changes the site collection back to normal.