It appeared the the username, access codes etc were correct within the pp_confirm.php page.
$Shipping_Parameters["Password"] = "xxxxxxxxxx";
$Shipping_Parameters["AccessKey"] = "xxxxxxx";
$Shipping_Parameters["ShipperNumber"] = "xxxxxxx";
But the shipping info was skipped in the checkout process and went directly to PayPal without and shipping costs.
I also have run checkout wizard with Pay Flow Link but the login, Merchant login, user name and password fields are not clear on which user names, passwords etc..
Login: Is this the main PayPal user account email ? Errors with "Username is required"
Merchant Login: Is this the PayPal Manager username or API username? "Errors with Password is required."
User: Is this the PayPal Manager username? Errors with "Signature is a required field".
Password: Is this the API password or PayPal Manager Password? Or? Password is not a required field.
I have tried many combinations, but haven't been able to get it. Don't know if it is just my misunderstanding of what is required or the extension.