Cart information is stored in session variables.
When A session is started, a cookie is created on the client computer to track the session.
cookies are based on domains.
the problem you are having is that you are crossing domain between the checkout page and eCart page when paypal returns you.
When you are at:
checkout.php
you are are on one domain:
www.primefloridaland.com
'
paypal is returning you to:
ecart.php
which is a differant domain:
primefloridaland.com
there is no www.
as far as session cookies are concerned, these are two separate domains, with 2 separate sessions.
on the confirm page, set the return URL to use the domain.