I'm running Zen 1.3.8a and PayPal Express Checkout. I have "PayPal Express Checkout" installed and enabled, Paypal Standard is NOT installed.

When purchasing only gift certificates, the PayPal transaction is not created.
I tested in debug mode. See some results at end of this post.
It appears that because there no required shipping, the address is not sent to PayPal and the transaction doesn't complete.


Debugging
ec_step2_finish - 2
Code:
    country_id = 223  
  address_format_id = 2
  state_id = 0 (original state tested: )
  country1->fields['countries_id'] = 
  country2->fields['countries_id'] = 
  $order = stdClass Object
  (
      [customer] => Array
          (
              [name] => Shakur Ali
              [company] => 
              [street_address] => 
              [suburb] => 
              [city] => 
              [postcode] => 
              [state] => 
              [country] => Array
                  (
                      [id] => 223
                      [title] => 
                      [iso_code_2] => 
                      [iso_code_3] => 
                  )
   
              [format_id] => 2
              [email_address] => n AT musikdebu DOT com
              [telephone] => 
              [zone_id] => 0
          )
   
      [billing] => Array
          (
              [name] => Shakur Ali
              [company] => 
              [street_address] => 
              [suburb] => 
              [city] => 
              [postcode] => 
              [state] => 
              [country] => Array
                  (
                      [id] => 223
                      [title] => 
                      [iso_code_2] => 
                      [iso_code_3] => 
                  )
   
              [format_id] => 2
              [zone_id] => 0
          )
   
      [delivery] => Array
          (
              [name] => Shakur Ali
              [company] => 
              [street_address] => 
              [suburb] => 
              [city] => 
              [postcode] => 
              [state] => 
              [country] => Array
                  (
                      [id] => 223
                      [title] => 
                      [iso_code_2] => 
                      [iso_code_3] => 
                  )
   
              [country_id] => 223
              [format_id] => 2
              [zone_id] => 0
          )
   
  )