This happens when the Name Servers listed for the domain name are either not authoritative for the domain name or the Name Servers are not on different subnets. Two subnets differ from each other if at least one of the first 3 segments of the IP address is different.
The .DE Registry requires this to be corrected within 30 days or they cancel the registration with no refund given.
If the Name Servers are correct you will need to contact your Domain Provider and have them create a Zone file for your domain name on the name servers listed.
Once they have confirmed this has been done you will need to log into a Domain Management Interface registry re-validate the domain. This is located under the option “Domain Extras”.
Otherwise you will need to change the name servers via the “Manage Name Servers” section of a Domain Management Interface.