[caseyf]

Try PayPal's Merchant Technical Support (https://ppmts.custhelp.com/app/ask - Mass Pay is under "API Products") The developer forums on x.com can sometimes be helpful as well. They have a few staff members that work the boards.

If you're a developer, you don't really want to use their front line Customer Service.

It also helps to have an account manager but how you get one is a mystery. They called us up one day and said, Hi! I'm your new account manager.