Error trying to checkout as a customer on my website

[winningodds]

Hi,

I have just connected paypal to my website. I have put my merchant ID and email in the API section on my membership system on my website. I tried to test the membership system on my website by trying to make a purchase using my personal paypal account but when i try to do so, it gives me the following error:

I would greatly appreciate it if someone could help me. It really would mean so for me to get this problem fixed. 

Thanks in advance