When you update any theme/plugin on a WordPress site, usually you will see a screen like this if the update process goes well.
Sometimes, this process will not get completed and it will get stuck at the following step:
and when you when you check the site at front end, it will show this message
The most probable reasons for this issue are:
You tried updating too many plugins/theme at once.
Any of the theme/plugin update has a conflict with other plugin/theme causing the update process to fail.
Solution: You need to go to the root folder of your hosting file mangers(public_html folder) via FTP or cPanel and you will see a file called .maintenance there. You just need to delete this file to fix the issue and bring back the site.
Note: If you do not see this file in the root folder, please make sure you have enabled the viewing of hidden files from the file settings in your hosting file manager as most of the hosts keep a file hidden if it is started with a dot. If you are not comfortable editing any files on your website then you will need to contact your web host for further assistance.
We also have a great in depth blog post on troubleshooting here.