“Briefly unavailable for scheduled maintenance. Check back in a minute” is an error in WordPress, which usually occurs when an update is running.
This white screen and this line are just a way for WordPress to notify website visitors that there is some maintenance (updates) going on.
However, if you see this “Briefly unavailable for scheduled maintenance. Check back in a minute” error message on your WordPress website and you have not updated any of the above mentioned, that means that one of the previous updates failed and now the WordPress is stuck in maintenance mode.
Before I get to the actual steps on how to fix “Briefly unavailable for scheduled maintenance. Check back in a minute” error in WordPress, it’s important to say, you should always create a backup before messing with the code.
Delete .maintenance file
Step 1. Using nd FTP Program or cPanel’s FIleManager, log in to your WordPress’s installation directory…
Step 2. Locate a file called .maintenance and delete it!
Step 3. Now go back to the front page of your website and refresh the page to check if the error is gone.
Sometimes if the WordPress core upgrade failed, you will see a “Database Update Required” message after logging into wp-admin area.
Simply follow the instructions and update your WordPress database.
NOTE: create a backup before the database upgrade!