how to fix error “called incorrectly, should not be accessed directly”?

I was able to figure out the issue. it was coming from the credit card processor. Our credit card was expired and account wasn’t updated, so they disabled our account, not allowing us to process transactions through their gateway.

The company we use is Plug n Pay

The error ending with “C: nonp” represents “non-payment”.

Hope this helps someone else who runs into this.