WordPress creates a file named .maintenance in the root while it updates, and deletes it when finished. If an update is interrupted, the file is left behind and the site stays stuck on the maintenance notice.
The fix
- In cPanel open File Manager and go to
public_html. - Click Settings (top right) and tick Show Hidden Files (dotfiles).
- Find the file named
.maintenanceand delete it. - Reload your site.
Finish the interrupted update
The update did not complete, so log in and go to Dashboard → Updates and run it again. If the site now shows errors, the partially-updated plugin is probably at fault — reinstall it fresh.
Preventing it
Update a few plugins at a time rather than all at once, do not close the browser tab mid-update, and make sure your PHP max_execution_time is at least 300 so large updates have time to finish.