Hi Matthew,
I understand your frustration, but don't worry, we'll find a solution to your issue. From what you've described, it seems like you've taken the right steps so far in setting up your domain. However, there could be a few things we can check to troubleshoot the problem.
Firstly, ensure that the network configuration between your computers and the domain controller is correct. Make sure that all the computers are on the same subnet and are using the correct IP address for the domain controller as the primary DNS server. Double-check the subnet mask and default gateway settings as well.
Next, verify that the Windows Firewall or any other security software on the domain controller is not blocking the necessary network traffic. You might need to temporarily disable the firewall or create inbound rules to allow communication with the domain controller.
Additionally, check the time synchronization between the domain controller and the client machines. If there is a significant time difference, it can cause authentication failures. Ensure that all the computers are set to the correct time and time zone and that they are synchronized using the same time server.
Now, let's verify the DNS settings on the domain controller. Make sure that the DNS server is configured with the appropriate forward and reverse lookup zones for your domain. The domain controller's IP address should be the primary DNS server for the clients, and it should be able to resolve the domain name correctly.
You mentioned that you can ping the domain controller, but can you try pinging the domain name as well? Open a command prompt on one of the client machines and run the command: "ping yourdomainname". If it resolves to the correct IP address of the domain controller, that's a good sign.
If none of the above steps solve the issue, it would be helpful to check the Event Viewer on both the domain controller and the client machines for any relevant error messages. These messages might provide more insights into the specific issue causing the "Domain not available" error.
I hope these suggestions prove helpful in resolving your problem. Please feel free to provide more information or ask further questions if needed.