Fatal error: Uncaught RuntimeException: FTP hostname is required in /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php:1349
Stack trace:
#0 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(1398): Cache_Enabler_Disk::get_filesystem()
#1 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(437): Cache_Enabler_Disk::mkdir_p('/var/www/html/w...')
#2 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(1168): Cache_Enabler_Disk::create_settings_file(Array)
#3 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_engine.class.php(91): Cache_Enabler_Disk::get_settings(true)
#4 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_engine.class.php(26): Cache_Enabler_Engine->__construct()
#5 /var/www/html/wp-includes/class-wp-hook.php(353): Cache_Enabler_Engine::start('')
#6 /var/www/html/wp-includes/class-wp-hook.php(377): WP_Hook->apply_filters(NULL, Array)
#7 /var/www/html/wp-includes/plugin.php(523): WP_Hook->do_action(Array)
#8 /var/www/html/wp-settings.php(779): do_action('init')
#9 /var/www/html/wp-config.php(139): require_once('/var/www/html/w...')
#10 /var/www/html/wp-load.php(50): require_once('/var/www/html/w...')
#11 /var/www/html/wp-blog-header.php(13): require_once('/var/www/html/w...')
#12 /var/www/html/index.php(17): require('/var/www/html/w...')
#13 {main}

Next RuntimeException: There was an error initializing the WP_Filesystem class: FTP hostname is required in /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php:1362
Stack trace:
#0 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(1398): Cache_Enabler_Disk::get_filesystem()
#1 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(437): Cache_Enabler_Disk::mkdir_p('/var/www/html/w...')
#2 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php(1168): Cache_Enabler_Disk::create_settings_file(Array)
#3 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_engine.class.php(91): Cache_Enabler_Disk::get_settings(true)
#4 /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_engine.class.php(26): Cache_Enabler_Engine->__construct()
#5 /var/www/html/wp-includes/class-wp-hook.php(353): Cache_Enabler_Engine::start('')
#6 /var/www/html/wp-includes/class-wp-hook.php(377): WP_Hook->apply_filters(NULL, Array)
#7 /var/www/html/wp-includes/plugin.php(523): WP_Hook->do_action(Array)
#8 /var/www/html/wp-settings.php(779): do_action('init')
#9 /var/www/html/wp-config.php(139): require_once('/var/www/html/w...')
#10 /var/www/html/wp-load.php(50): require_once('/var/www/html/w...')
#11 /var/www/html/wp-blog-header.php(13): require_once('/var/www/html/w...')
#12 /var/www/html/index.php(17): require('/var/www/html/w...')
#13 {main}
  thrown in /var/www/html/wp-content/plugins/cache-enabler/inc/cache_enabler_disk.class.php on line 1362