PCI :: Error during transaction on Authorize.net integrated form

I am getting the same error

http://www.buttonmakers.net/Pay-an-Invoice_ep_48-1.html

As I tried to submit the form using a test credit card number, I see that the following error is displayed.

Looking at the Authorize.net documentation, this error occurs due to incorrect setup at the processor.

https://www.authorize.net/support/merchant/wwhelp/wwhimpl/common/html/wwhelp.htm#context=Merchant_Integration_Guide&file=4_TransResponse.html

Please make sure that you are using the correct API and Transaction keys. Also, please try generating a new transaction key and see if that helps. You may also check with Authorize.net if there is any issue with the account.

Let us know if you need any further assistance. We will be happy to assist.  

You are right. The API key had expired. Thanks for your time. 

Rebecca