I was updating a couple of plugins in this WordPress site, which I usually do when I get update notifications with no issues. This time however the message in the screenshot below appeared and would not go away.
To fix this, you need to rename or delete the .maintenance file.
Login to cPanel and click on File Manager
Click on the public_html directory
The file is hidden (it’s preceded with a .), so to view hidden files click on Settings on the top right of the page.
Check the Show hidden files box and click save
You will now see the .maintenance file, rename or delete it and you should be able to access your site again.