Cant Map a Domain to my sub domain in Multisite WP

Hi, i can't map my domain nlp-lobby.de to my WPMU Subsite http://rosenbauer-immobilien.ihre-immobilienmakler-webseite.com/

I have alread create the right dns A record with my Server IP but i get an error by mapping ther domain.

Domain name is unavailable to access.

nslookup to the domain returns the Server IP from my WPMU site.