I have same issues
What was the outcome to this problem as I have the same problem.
Powerstore 3 Ecart5
When I click on Paypal button I go to Paypal site. Log In and go back to Order Confirmation page on my site. No Paypal Express info is showing and only a comma in Shipping Info.
When I Submit Order I go to pp_Checkout_failure.php which states:
"we're sorry your transaction could not be completed. Please return to checkout and try again"
I tried posting the code into the pp_Checkout_failure.php page but no further information shows.
I get the same results if I use credit card rather than logging into my Paypal account.
I am testing this live.