OK, I'm getting close. I got the credentials from PayPal. I put the into the PowerStore settings. The PayPal button appears on the checkout page. But when you click it, it doesn't take you anywhere.
I took the store out of test mode. I've tried checkout with or without debug mode and see no difference.
One odd thing is that on the store settings page, when I click to save, it momentarily flashes and shows the payment gateway info and then that goes away and it returns to the store settings page.
I'd be happy to give you the admin login if you wanted to look and see.