You would have to go to your domain registrar and use the two Cloudflare name servers instead of the four ui-dns ones. Sometimes this is tricky for .de domains, but give it a try at denic.de (if that’s your registrar).
I thought it would be the usual registry validation issue and guess what, it is the usual registry validation issue
@champlife, your domain must be still associated with another Cloudflare account which comes with the nameservers adel and zod, whereas your current account assigned bob and lorna. The .de registry is one of those few (.dk and .it as well) who believe they need to verify the nameservers and that wont work in this context.
Long story short, use the previous account if possible. If not remove the domain from there and if that is not possible either you can only contact either your registry or Cloudflare and have one of them the values set forcibly.