Hi, 

We are using the gravity form plugin and gravity form authorize.net addons plugin

We cannot pass through the registration process because the credit card information always sending this error

: There was an error processing your credit card. Please verify the information and try again.

We are using the test account on authorize.net sandbox as API and key, the credit card that we are using also came from authorize.net sandbox

What might be the problem that causing this.

Thanks