Cannot add new domain, already used by another Netlify user

Hi,
We are trying your platform and we wanted to add domain tring.si. But when adding this, it says it’s already used by another user. We cannot add it although we’re owning this domain and to setup DNS records this means we cannot proceed. What do we do in this situation?
Thanks in advance!

This should be resolved.

Thank you for your support during the weekend!