The following error appears when a SiteGround hosting account has reached its “Inode Quota Limit.” Apparently, this limit disables certain functionality on the account, which breaks this plugin in a bad way.
Given that this plugin is a SiteGround product, I would expect it to not fail so spectacularly when a SiteGround limitation is in place.
Fatal error: Uncaught TypeError: ftp_nlist(): Argument #1 ($ftp) must be of type resource, null given in /home/customer/www/{domain.tld}/public_html/wp-admin/includes/class-wp-filesystem-ftpext.php:427 Stack trace: #0 /home/customer/www/{domain.tld}/public_html/wp-admin/includes/class-wp-filesystem-ftpext.php(427): ftp_nlist(NULL, ‘/home/customer/…’) #1 /home/customer/www/{domain.tld}/public_html/wp-admin/includes/class-wp-filesystem-base.php(229): WP_Filesystem_FTPext->exists(‘/home/customer/…’) #2 /home/customer/www/{domain.tld}/public_html/wp-admin/includes/class-wp-filesystem-base.php(58): WP_Filesystem_Base->find_folder(‘/home/customer/…’) #3 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Htaccess/Htaccess.php(114): WP_Filesystem_Base->abspath() #4 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Htaccess/Htaccess.php(81): SiteGround_Optimizer\Htaccess\Htaccess->set_htaccess_path() #5 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Install_Service/Install_5_0_0.php(29): SiteGround_Optimizer\Htaccess\Htaccess->__construct() #6 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Install_Service/Install_Service.php(59): SiteGround_Optimizer\Install_Service\Install_5_0_0->__construct() #7 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Helper/Factory_Trait.php(32): SiteGround_Optimizer\Install_Service\Install_Service->__construct() #8 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Loader/Loader.php(208): SiteGround_Optimizer\Loader\Loader->factory(‘install_service’, ‘install_service’) #9 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/core/Loader/Loader.php(118): SiteGround_Optimizer\Loader\Loader->load_dependencies() #10 /home/customer/www/{domain.tld}/public_html/wp-content/plugins/sg-cachepress/sg-cachepress.php(72): SiteGround_Optimizer\Loader\Loader->__construct() #11 /home/customer/www/{domain.tld}/public_html/wp-settings.php(453): include_once(‘/home/customer/…’) #12 /home/customer/www/{domain.tld}/public_html/wp-config.php(120): require_once(‘/home/customer/…’) #13 /home/customer/www/{domain.tld}/public_html/wp-load.php(50): require_once(‘/home/customer/…’) #14 /home/customer/www/{domain.tld}/public_html/wp-admin/admin.php(34): require_once(‘/home/customer/…’) #15 /home/customer/www/{domain.tld}/public_html/wp-admin/index.php(10): require_once(‘/home/customer/…’) #16 {main} thrown in /home/customer/www/{domain.tld}/public_html/wp-admin/includes/class-wp-filesystem-ftpext.php on line 427