The lab assignment for installing and setting up Active Directory and promoting a server to a DC has a possibly incorrect instruction. When modifying the server network settings from a DHCP assigned value to a static IP, the instructions say to set the SUBNET mask to 10.0.0.0/8
The server will not accept this subnet value. Actually, after entering the server IP, it auto-suggests a subnet of 255.0.0.0. Taking this suggestion continues the configuration process, and I completed the setup as a result.