Paypal Pro Sandbox Setup Help

I'm trying to configure a Paypal Pro Sandbox account for testing on my testing site. I have all the info setup correctly under Payment methods, but I'm getting the error.





[center]Security header is not valid[/center]





or



The transaction could not be loaded

[center][color=#FFFFFF][font=OpenSansRegular, Helvetica, sans-serif][size=3]The transaction could not be loaded[/size][/font][/color][/center]



Currently I'm using “Test Mode”, doesn't seem to work any better in live mode either.





Using Regular paypal seems to work ok since I see the orders in my email inbox in Paypal. But I'm not getting an order confirmation from the cart, but from paypal itself.



Any ideas?

Are you using Paypal Pro or Paypal's Payflow Pro?

i am having same sets of errors and i am using paypal pro.

I use PayFlow Pro with live mode