When I look at the HTML, I see the code is there (so the shortcode is being interpretted) but it looks like there is a quote (") missing after the encrypted characters. Have a look here http://www.eurocalifornia.org/test-button-page/
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_s-xclick" />
<input type="hidden" name="encrypted" value="-----BEGIN PKCS7-----MIILAQYJKoZIhvcNAQcEoIIK8jCC..........{lots of the encrypted code deleted}...........z9QCf/fRJA==-----END PKCS7-----<br />
” /><br />
<input type="image" src="https://www.paypal.com/en_US/i/btn/btn_xpressCheckout.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!" />