PayPal button encryption not working

HI Folks...
I have set up encryption on my PayPal buttons...downloaded all the API information, ticked the right boxes both In S2 and PayPal. However when I produce the PayPal button and try to test it Paypal advises that they only use encrypted buttons and won't let me in. Can you tell me what I am missing at all?
I have set up encryption on my PayPal buttons...downloaded all the API information, ticked the right boxes both In S2 and PayPal. However when I produce the PayPal button and try to test it Paypal advises that they only use encrypted buttons and won't let me in. Can you tell me what I am missing at all?