What is needed to make Payflow Pro Recurring Donations work?
This issue from 2009 seems to be the one to add payflow into the core:

https://issues.civicrm.org/jira/browse/CRM-5536

per Eileen comment:


  "Although the code is there to upload recurring transactions the
  customer opted not to complete the recurring payment side of things so
  this should be turned off in the payment_processor_type table for now.
  
  (code works but on-going querying of outcomes in incomplete)."


I would suggest you add a comment to this issue or contact Eileen on chat.civicrm if you want to know more about what's missing or an estimate of the number of hours need to make the recurring happen