On the settings page, add “bn=1″ to the Buy Now URL and the 1 Step Checkout will work.

If you are using the masked domain url, it would look like –

http://www.example.com/cmd.php?bn=1

If you are NOT using the masked domain url, it would look like –

http://www.mcssl.com/SecureCart/SecureCart.aspx?mid={Your MID}&bn=1

Please note the “?” versus the “&” preceding the variable (bn) in each of these examples.