An error occured when validating interfaces

Hello,

I am setting up an DA Server with two Network interfaces. They are already configured with static IPv4 Adresses.

I am going in the Remote Access Management Console > DirectAccess and VPN > Step 2 "Edit" > Network Adapters

Its equal if an adapter is selected or not it tells me every time this error: An error occured when validating interfaces

Technet says in the "Step 1: Configure the DirectAccess Infrastructure" Tutorial:Ensure that the second network adapter and any additional network adapters are classified in the domain profile.

What does that mean? What do i have to do?

I would be very thankful if someone could help me.