How do I fix a broken “Agree to Terms and Conditions” checkbox that blocks checkout?

A broken terms checkbox happens when the form validation script fails to register the checked property status of the HTML element, locking customers out of checkout even after they click the box.

“Most minor website breaks are caused by simple script conflicts, legacy code blocks, or broken API handshakes. We identify and clear these issues immediately as a straightforward, one-time fix.”
— Jeff Bollettino, Managing Director, Ignite Conversions