Oh no! You get this message on every single page of your WordPress site including the Admin area.
Briefly unavailable for scheduled maintenance. Check back in a minute.
It’s likely you were doing an update of WordPress or a WordPress plugin/theme and something went wrong or maybe you interrupted the process by closing your browser window.
Simply login to your server and in the root of your WordPress directory you’ll see a file called `.maintenance`. Delete it… yes, just delete the file called `.maintenance`.
Now your site is back up and you’ll be able to access the WordPress Admin area again. Just remember that when you’re doing a WordPress software updates, wait for the confirmation screen before clicking on something else or leaving the page.