Google reCAPTCHA token is missing

I am trying to add a credit card to my account on a vendor's website. After providing all the required information I receive the error message, "Google reCAPTCHA token is missing".

I have tried this in Safari in macOS 15.7.2 in normal and private windows, in Safari in iOS 18.7.2, and even in Firefox on macOS. I've followed recipes available online to disable various security features and apps that prevent cross-site browsing and the like.

Has anybody run across and solved this problem?