Fatal error: Uncaught Error: Undefined constant "MB_OVERLOAD_STRING" in /home/.sites/59/site1900/web/cms3/libraries/vendor/joomla/string/src/phputf8/utf8.php:38
Stack trace:
#0 /home/.sites/59/site1900/web/cms3/libraries/vendor/composer/autoload_real.php(66): require()
#1 /home/.sites/59/site1900/web/cms3/libraries/vendor/composer/autoload_real.php(56): composerRequire205c915b9c7d3e718e7c95793ee67ffe('2fb9d6f23c8e8fa...', '/home/.sites/59...')
#2 /home/.sites/59/site1900/web/cms3/libraries/vendor/autoload.php(7): ComposerAutoloaderInit205c915b9c7d3e718e7c95793ee67ffe::getLoader()
#3 /home/.sites/59/site1900/web/cms3/libraries/cms.php(36): require('/home/.sites/59...')
#4 /home/.sites/59/site1900/web/cms3/includes/framework.php(18): require_once('/home/.sites/59...')
#5 /home/.sites/59/site1900/web/cms3/index.php(40): require_once('/home/.sites/59...')
#6 {main}
  thrown in /home/.sites/59/site1900/web/cms3/libraries/vendor/joomla/string/src/phputf8/utf8.php on line 38