Original article address (invasion) http://https://www.wpdaxue.com/briefly-unavailable-for-scheduled-maintenance.html
WordPress will first switch to maintenance mode when upgrading programs, themes, and plug-ins. It means "Briefly unavailable for scheduled maintenance. Check back in a minute" is displayed. If the upgrade goes smoothly, it will return to normal in a few seconds; but if it is due to poor internet speed, etc. If the upgrade is interrupted due to the reason, WordPress will always stay in maintenance mode, regardless of whether it is in the foreground or the background, it will always display "Routine maintenance is being performed, please come back in one minute".
How to solve this problem?
1. Immediately log in to your website via FTP, delete the .maintenance in the WordPress root directory, and refresh the page.
2. But sometimes you will find that the root directory does not have .maintenance at all! Changmeng encountered this problem recently. At first, I thought it was hidden, so I used SSH to log in to the server, but I still didn't see it. What should I do? In fact, there is a relatively simple way, directly create an empty txt text, upload it to the host space, and then rename it to .maintenance, and then you will find that the .maintenance is missing! Don't worry, refresh your website again, is it normal? !