Authorize.net: Why am I getting transaction declined message?

We've recently had several forms that are giving users a PCI Error when that try to send in the form with a credit card transaction. 

We use Authorize.net and I've checked out API Code and Transaction codes and they are correct. 

Any suggestions?

I have cloned your form and integrated it with Authorize.net on my end, I can see the form works fine and it submits without any problem. 

You could try on this form: https://form.jotform.com/70717345983970 

Enter this testing payment info: 

- Credit Card Number: 4242424242424242

- CVC : 123

- Valid Expiration Date

  *Later than the current date

But my integration is set to sandbox mode, this is why it accepts the testing credit card info. 

I have also checked on Authorize.net documentation and found this related article to the error you're receiving: https://support.authorize.net/authkb/index?page=content&id=A59 

I would suggest you to either try your integration on sandbox mode, here's a guide that will help you with that: https://www.jotform.com/help/221-How-to-Test-Authorize-net-Payment-Tool-on-Sandbox-Mode 

And make sure you're entering a valid credit card info, otherwise the payment will not be processes. 

Hope this helps.