Hetzner has another way to use API keys, there is no global API key. You will have to create a project and request a token for that project to create the server in. Make sure you create a new Project first in your account.
Next access this project, and go to "Access" on the left. Next navigate to the "API TOKENS" tab and generate a new token.
EXTRA: If you want extra security you can allow this API address as only access to that token: -Hidden-