Try creating a paypal transaction, then have your cart go to PayPal, then hit the Cancel option to return to your site. If you can return successfully back to your cart without any problems, then it is likely the customer cancelling the return back to your site after the transaction is completed. A known problem with PayPal. You then manually have to type True in the field.

Alternately, if you cannot return back to your site, then I think there is an unaddressed issue in the cart. I believe a return url is being passed back to PayPal and that is overriding the return url you set in PayPal settings.... this causes the url to show as http://yoursite.com:443 instead of a regular https link.

I kind have been waiting for a fix on this... I have been stuck on this for 3 months now! Why does the return to our site not come back as https, but as the url and :443.

Steve