[opensuse] "No ReCAPTCHA response provided" error message

I tried to join a mailing list and received "No ReCAPTCHA response provided" message. How does one get Thunderbird, or Firefox to return the desired response? I assume it is Thunderbird, since it is a mailing list. Never hit this one before. Don -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org