Kristian I suspect, but can't be sure, Eventbrite is at fault for not yet having implemented the latest version of Mastercard 3DSecureCode/Identity Check, this new version is necessary in Europe as of this year (PSD2, SCA rule) and ensures safe payments.
However, it still happens that websites and psp's are behind on the code to support the latest standard.
Have you contacted Eventbrite themselves about this yet?
PSD2: Payment Service Directive 2
SCA: Strong Costumer Authentication.