Today I got one of my MultiSites stuck in Maintenance mode while updating plugins. I couldn’t access any of the sites. All I got was that maintenance mode message. I looked up a solution, this was simple and it worked.
This is copied from an old WordPress Support Forum Post, the green text worked.
My installation of WordPress 3.9.1 i stuck in Maintenance mode, and I can’t get it out. Can anyone help me?
Try deleting the file called “.maintenance” in the root of the site’s web folder. That should disable the maintenance mode.
It does not have one.
– It is a hidden file like .htaccess files. You can delete it using FTP program or loging in server and select to view hidden files.