IIS & other services have suddenly stopped working on my EC2 windows m6a.xlarge instance

Based on the symptoms you've described, it appears that your EC2 Windows instance is experiencing some serious issues that are affecting multiple services and features. This could be due to a combination of factors, and it's important to investigate thoroughly to determine the root cause.

Here are some steps you can take to troubleshoot and potentially resolve the issue:

1. Check instance status: First, ensure that your instance is listed as "Running" in the Amazon EC2 console and that it's passing all status checks. If it's not, this could indicate underlying hardware or connectivity issues.

2. Investigate system resources: Although you mentioned that CPU and RAM usage are low, and there's still free disk space, it's worth double-checking these metrics using Amazon CloudWatch or other monitoring tools to ensure there isn't an unexpected spike in resource usage.

3. Review system logs: Use the EC2 console to access the instance's system log and look for any error messages or warnings that might indicate what's causing the services to fail.

4. Use EC2Rescue for Windows Server: This is a powerful tool provided by AWS for diagnosing and troubleshooting Windows instances. You can download and run this tool on your instance to collect logs and other diagnostic information. This might provide insights into why IIS and other services are not functioning.

5. Check for Windows updates: Although unlikely to cause such widespread issues, ensure that your Windows instance is up-to-date with the latest patches and updates.

6. Verify EC2Config service: Make sure the EC2Config service is running and up-to-date. This service is crucial for proper functioning of EC2 Windows instances.

7. Examine Windows Event Logs: If you can access the Event Viewer, check for any critical errors or warnings that might explain the service failures.

8. Consider file system issues: Although you have free space, there might be file system corruption. You may need to run a disk check utility if possible.

If these steps don't resolve the issue or provide more information about the problem, you may need to consider more drastic measures such as:

1. Creating a new EC2 instance from a recent backup or snapshot.
2. Detaching the EBS volume and attaching it to a healthy instance for further investigation.
3. Contacting AWS support for more advanced troubleshooting assistance.

Given the sudden and widespread nature of the issue affecting multiple core Windows services, it's likely a Windows-related problem rather than an AWS-specific issue. However, the underlying cause could be related to instance hardware, networking, or other EC2-specific factors that are impacting the Windows operating system.
Sources
Troubleshoot EC2 Windows instance status check failures | AWS re:Post
Troubleshoot Amazon EC2 Windows instance start issues - Amazon Elastic Compute Cloud
Troubleshoot website connectivity on EC2 Windows instance | AWS re:Post
Troubleshoot impaired Windows instance with the EC2Rescue GUI - Amazon Elastic Compute Cloud