I get the Service Unavailable when trying to add a new admin user or customer. Right now I only have the administrator user from installation. I do have an Avalara sales tax module installed which required core modifications. But, the only one in this list is the profiles.php.
I've checked other cscart sites and none of them have a user with id 0.
Database (error) Error:You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM cscart_users WHERE user_id = 0' at line 1 (1064) Query:SELECT FROM cscart_users WHERE user_id = 0
/**
* Prepare params for getting user info query
*
* @param string $condition Query condition; it is treated as a WHERE clause
* @param int $user_id User identifier
* @param array $user_fields Array of table column names to be returned
*/
fn_set_hook('get_user_info_before', $condition, $user_id, $user_fields, $join);
$user_fields = implode(',', $user_fields);
$user_data = db_get_row("SELECT $user_fields FROM ?:users $join WHERE user_id = ?i $condition", $user_id);