Using FTP or the cPanel->File Manager you can check if there is a “.maintenance” file in the public_html folder and delete it. Or if its not the main primary cPanel domain, then in the website folder for the domain in question.
Means the WordPress update didn’t delete that .maintenance file after the update, the reason may be related to a plugin or theme update.
If using cPanel->File Manager to delete the .maintenance file, make sure the File Manager settings are set to view the hidden files ie. .maintenance has the period at the start means it’s hidden.
