Fatal error: Uncaught Error: Call to undefined function FacebookAds\Http\Adapter\mb_substr() in /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Http/Adapter/CurlAdapter.php:104 Stack trace: #0 /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Http/Adapter/CurlAdapter.php(189): FacebookAds\Http\Adapter\CurlAdapter->extractResponseHeadersAndBody('HTTP/2 200 \r\nva...') #1 /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Http/Client.php(204): FacebookAds\Http\Adapter\CurlAdapter->sendRequest(Object(FacebookAds\Http\SimpleRequest)) #2 /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Object/ServerSide/AdsPixelSettings.php(85): FacebookAds\Http\Client->sendRequest(Object(FacebookAds\Http\SimpleRequest)) #3 /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Object/ServerSide/AdsPixelSettings.php(62): FacebookAds\Object\ServerSide in /home/itsteps/public_html/system/library/vendor/facebook/php-business-sdk/src/FacebookAds/Http/Adapter/CurlAdapter.php on line 104