Testing PayPal certificate on a different domain

I have a PP-enabled site that needs to be tested. I've already tested it with Sandbox credentials and it works ok. The next step is to test it with live PayPal credentials on test server. Here I hit a wall, because using real credentials from liveserver.com on test.liveserver.com gives me error of "malformed url" (whic开发者_如何学Ch as I read stands for "invalid credentials").

And here is the question: are PayPal credentials domain-bound? Can I get error message because I am using live api credentials on a subdomain(different domain)?

The same PayPal SSL certificate can be used on subdomains too.