I tried setting up paypal express. I've added the correct parameters. I then go to checkout and it says
 
"Now you will be redirected to (my cart). If nothing happens please click 'Continue' button to proceed."
 
It takes a while then I get this error
 
"Empty response from PayPal, please check that your payment parameters Username, Password and SSLCert were set correctly. "
 
The parameters appear to be correct. Do I put Get or Post? What about the 'Not Passed' checkmarks? Do I leave them checked or not? Is there something else I should do to the checkout page? Please don't refer me to the paypal express page.. I know various people have had empty repsonse questions. Someone pleaase help. Thank you

To also mention, I'm using godaddy as my host. Can anyone help?

I am setting up Paypal Express too ... and am having difficulty. When checking out using Paypal Express, I do not receive an error message ... the browser goes to the home page of the cart and nothing else happens. Any suggestions?