The following steps can help you troubleshoot an Active Directory domain controller not responding:
- Check if basic network connectivity is functioning
- Confirm if the Domain Controller can communicate with other domain controllers
- Check if any events related to the Domain Controller are present in the Directory Services or System Event Logs
- Check if the Domain Controller is receiving the latest updates and patches
- Ensure the Domain Controller is configured properly (role, FSMO, etc.)
- Run the AD replication test to identify replication issues
