Starting with version 3.7, WordPress can automatically perform minor updates. But sometimes, because of low memory or some other server errors, this update may put your site in maintenance mode, displaying Briefly Unavailable for Scheduled Maintenance Error. Well, don’t panic. It’s easy to fix.
does this happen?
During the update, WordPress creates a .maintenance file in the root directory of your WordPress installation. Normally, WordPress automatically removes this file after the update. If the update fails to remove .maintanance file for some reason, you will see this error.
How to fix?
Fixing this is quite easy. Go to the root directory of WordPress installation and remove
If this doesn’t solve your issue, you may need to manually update WordPress. Refer this post for the instructions for manually updating WordPress.