The only problems the server scanner found were:
Error[ERROR] MySQL Database Extension
Missing MySQL extension. s2Member needs the MySQL extension for PHP. This will add MySQL support to your installation of PHP, allowing MySQL database communication. Please consult with your web hosting company about this message.
Error[ERROR] Mcrypt/Encryption Extension
Missing Mcrypt extension. s2Member needs the Mcrypt extension for PHP. This will add encryption support to your installation of PHP, with a variety of block algorithms; such as DES, TripleDES, and Blowfish. Please consult with your web hosting company about this message.
My host is using mysqli and mysqlnd and says Mcrypt was removed from PHP 7.2 after being deprecated in 5.5.
They had me downgrade to PHP 5.6 to see if that helped but it made no difference.