Be aware that using strong customer authentication methods such as Securecode/3Ds becomes mandatory when taking payments from European customers after 14 September 2019.
For subscriptions the first payment should be authenticated, but subsequent payments do not.
So all merchant payment gateways should be updated, or payment processing will simply stop working.
See the articles published by the various payment gateways for details. E.g.: https://stripe.com/en-US/guides/strong-customer-authentication