- get the url of the script you created (should look like https://raw.github.com/YOUR_USER_NAME/nixos-install-scripts/YOUR_BRANCH_NAME/hosters/hetzner-cloud/nixos-install-hetzner-cloud.sh).
if you copy and paste a url from the Hetzner console GUI, some characters can get replaced (If you are using an English/US keyboard layout for example). Just replace the offending characters (check the punctuation especially, @:_ and the likes).