In order to use Asset CleanUp Pro, you need to have the following:
WordPress site installed and active (not from WordPress.com, you need to have the open source software installed on your hosting package, the script from WordPress.org, see the differences here)
PHP 5.6+ (I strongly recommend PHP 7+ as it’s much faster and will boost the speed of your website considerably)
The plugin has been tested and is fully compatible with the latest PHP version: 8.1.