I had the same issue as Ryan H. My site is running multisite and removing lines 54-56 in the pardot.php file fixed the issue. (lines below).
/* This require is needed for wp_salt() which is used in the old method of decrypting if openssl is available
* otherwise we’ll get an undefined function error for wp_salt() during the password reencryption
*/
if ( !function_exists(‘wp_salt’) && defined( ‘ABSPATH’ ) && defined( ‘WPINC’ ) ) {
require_once ( ABSPATH . WPINC . ‘/pluggable.php’ );
}