An error in WordPress that results in the update not being completed as a result of interruptions that usually occur during the update. Probably “Briefly unavailable for scheduled maintenance. You'll see a warning like "Check back in a minute." But the site never opens. Everyone will see the same error.
How do we solve it?
Those who do not understand this error, the solution of which is quite simple, can wait forever if they implement the post. “Scheduled maintenance mode is unavailable. How to fix the "Check back in 1 minute" warning?
For this, you need to enter your hosting package and delete the ".maintenance" file in the main directory. This file is located in your WordPress directory. When you delete it, the error will go away.
In fact, this is not a mistake, as WordPress has become unavailable when updating, it should notify visitors that it is in maintenance mode. So it is normal that this warning appears. However, it is not normal for the person on the admin panel to see this error. This is due to the difficulty in updating. During the maintenance mode, the maintenance mode page that should be deleted at the end of the update is not deleted because the update cannot be completed and this error appears. If you delete it yourself, you can enter the admin page. Once you enter the admin page, you can do the update again.