If you visit your website straight after you click to update WordPress, your themes, or your plugins, you'll see a message that says "Briefly unavailable for scheduled maintenance."
This is the default message WordPress shows while it's running updates, and it's completely normal so don't worry!
Simply wait a couple of minutes for the update to complete and your site should return to normal. You may need to clear your browser cache, try in an Incognito window, or use a different browser to see the latest version of your website.
Occasionally, your site can get stuck in maintenance mode. If it's been more than a few minutes, especially if you only clicked to update one thing (as opposed to 10+ plugins), it's likely that the maintenance screen has got stuck.
If you're comfortable with FTP/file management, you can log in to your site's File Manager and locate and delete the file called .maintenance. If you'd prefer that we do it, simply raise a support ticket.