PayPal Failure

I am testing my checkout using PayPal Sandbox. I created the accounts, got the username and password and the signature, etc. When I click on the PayPal button, I get a failure page. I tried to troubleshoot by adding the Local Checkout Response behavior, but my list of behaviors does not include that one when I select that failure page in Dreamweaver.

The Ecart created two failure pages; pp_checkout_failure.php and checkout_failure.php. The latter page DOES show Local Checkout Response as an option when I click on Add Behavior, but the former does NOT. However, it is the former that comes up when I get the failure page described above, so I can't see what the error is.

How can I add a Local Checkout Response behavior to this page?

Ecart 5
Dreamweaver CS4