Hacker News Reader

Very likely Khan Academy can't help. Also your bank probably doesn't know why and neither does their fraud prevention service provider that runs some machine learning/AI system somewhere that decided to flag your transaction. At least that has been my experience in dealing with these things.

It is an unusual transaction, but we are living in unusual times. And the fraud detection process has not accounted for that yet.

Sorry to hear that. AFAIK, we just use Stripe, which is pretty standard.

I had a similar experience now. Never had to do reCaptcha on a payment form with my phone before. And then the payment was rejected. I am a normal US credit card payer. I ended up using PayPal.