I regenerated the API but no go! I called Paypal tech support and they deny that the API credentials could be bad. They keep insisting that the shopping cart is trying to use the sandbox with live credentials or live credentials with the sandbox. I checked everything tens of times and it should all be on the live credentials. I'm screwed. This site went live today and people are trying to order but can't. Can you open a support ticket and call me asap and see if you can pinpoint the problem for me?