Order for lack of insurance coverage, cars sold!

Hello people! I have a huge problem with the road traffic office. The following: on 27.02. I registered my Omega, registered in Viersen, at the road traffic office Düsseldorf. On the same day the car was sold and picked up, he is currently driving through Siberia. After a few weeks I demanded from the tax office the refund of the too much pay amounts. Response of the tax office: until now no cancellation has been received, please contact the road traffic office. Well, I got about 3 weeks ago. If the D’dorf Road Traffic Office asked to send a duplicate of the registration to the Viersen Road Traffic Office, this has also happened. Today I receive a payment note from the tax office about car taxes and from the Viersen Road Traffic Office an order for lack of insurance protection combined with an administrative fee, I should present registration plates etc. within three days at the Viersen Road Traffic Office. Sorry, but what are these sleeping caps? I know no Did anyone have a similar problem here? Thank you very much!