Capture Recaptcha fail event on Contact Form 7

You need to ask via Contact Form 7 support area. This place is not for

CT7 has a bunch of hooks/filters built in to their code. You’ll have to dig into their code to find them all. The docs that you can find about CF7 filter/hooks is third-party, and not well-maintained (many years old).

Asking CF7 for current filter/hook documentation will get you ‘crickets’, though…