I have not tried Hetzner but I tried Linode and the Linode website will reject my email address, my telephone number, and my street address as fraud due to problems with Linode’s automatic fraud detection system.
However, when I called up Linode’s 24/7 customer support, their friendly personnel named Kofi was very helpful and manually helped me register an account and even manually helped me get the $100 free credit. He told me that non American accounts have to handled manually.
So, please contact Hetzner and ask them why they “blacklisted” you and post that correspondence here so we all know for transparency reason.