One of the most annoying error in WordPress is the ‘Scheduled Maintenance’ message a Webmaster gets after an automatic upgrade has completed.

This problem is mainly caused by a failed automatic upgrade or an interrupted update process.  So each time a visitor tries to visit your home page, he/she will get the following message:

Briefly unavailable for scheduled maintenance. Check back in a minute.

In fact, each time WordPress is automatically updating its core files, themes or plugins, the blog will be  marked as ‘under maintenance’.
To fix this problem :  remove .maintenance (hidden) file, located  in your blog root directory and the site will come back.

maintenance

 

You may want to run the WordPress automatic upgrade again after resolving this problem.