UPDATED 7 May, 2018
Before you begin to use the Gravity Forms Paypal plugin, you must configure your settings with the PayPal website. This is really simple.
Navigate down your Dashboard to Forms
Click on the Forms link to open the fly-out menu
Click on the Settings link
This takes you to ….
Now click on the Paypal link
This takes you to a page where you’re asked to configure your PayPal settings
Click on the link and, from the next page, follow that new link to the PayPal website. Login.
It’s clear sailing from then on.