I already spoke to Paypal about this issue. I have a payflow account with them to allow recurring billing. Paypal is no longer allowing anyone to have a Legacy Payments Pro account that uses the old style DPRP which your Add-on is designed for. When I specifically asked paypal “How do I enable DPRP” they replied “You already have it – Payflow Recurring Billing.” I even told them how your app was designed to take API username, API password, and API signature and Paypal informed me that is no longer supported unless you have a legacy account and they are not allowing anyone to switch to a legacy Payments Pro account. The new Payflow API only requires a user name and password.
I believe the issue is with the add-on itself. It needs to be updated to use the current Paypal Payflow SDK and API system.
As for stripe… I am not a member. I am a buyer who has purchased a number of add-ons for my site from your company. We already use paypal, so I purchased the add-on to make things easy for us. I did not know the Add-on would not be compatible with our Paypal Payments Pro account.