I have a joomla website (https://cctvforum.id). Last week, it has not issue at all. But, when I open the website, the CSS is not running, even in the joomla admin site. I have no idea what caused it. I use joomla 3.3.3 and hathor admin template.
I can't even change the template via admin panel. Any help is greatly appreciated.
Did you see the error at the top of the page: The template for this display is not available. Please contact a Site administrator.
Looks like your template folder is gone or if you were using an alternative template, that this no longer exists. Check your filesystem for the templates folder. If it is no longer there, restore it from a backup.
The admin template can be found in the folder administrator/templates and if that is not there, you can get a copy from a fresh Joomla download.
Furthermore, you should really update your Joomla to the latest release which is 3.9.25.