If something goes wrong while updating a WordPress plugin or theme and the update fails, you may see the message “We are currently under maintenance and will be unavailable for a while.” message may appear.
When this message appears, maintenance mode is usually automatically canceled, but there may be cases in which maintenance mode is not canceled for some reason.
To manually remove maintenance mode in such a situation, delete the .maintenance file in the root directory of WordPress. This file tells the system that WordPress is in maintenance mode, so deleting this file will remove maintenance mode.