I've searched but not found this issue. We're trying to install and connect ShipStation.

Zen Cart 1.5.6a
PHP 5.6
(an upgrade of both is scheduled but PHP cannot be undated now)

ShipStation will not connect, I get a 401 error. The shipstation_zc.php file I got from them was an older version (1.5). I installed the new one (1.7) from here but get the same error.

The url enter is https and includes the www. just like the site files.

I tried commenting out the entire htaccess file but still got the 401 error.

Suggestions?