Facing problem while connecting ec2 instance

Hello.

Have you checked the troubleshooting tips in the following documentation?
There are several possible reasons why an RDP connection to EC2 may fail, so please check them out.
Common issues include misconfigured security groups or EC2 instances not being launched in public subnets.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/troubleshoot-connect-windows-instance.html

Based on the error message you're encountering, it appears you're having trouble connecting to your EC2 instance using EC2 Instance Connect. This is a common issue that can occur due to several reasons. Here are some steps you can take to troubleshoot and resolve the problem:

1. Security Group Configuration: The most likely cause is that your instance's security group is not properly configured to allow inbound SSH traffic (port 22) from the EC2 Instance Connect IP range for your specific region. You need to update your security group's inbound rules to allow SSH traffic from the EC2 Instance Connect IP range for your region.

2. Network Settings: Ensure that your EC2 instance is in a public subnet with an internet gateway attached. This allows for the necessary outbound traffic for Instance Connect to function properly.

3. Instance State: Verify that your EC2 instance is in the "running" state and not in a transitional state.

4. IAM Permissions: Check that the IAM user or role you're using has the necessary permissions to use EC2 Instance Connect.

5. EC2 Instance Connect Package: If you're using a supported Linux distribution, make sure the EC2 Instance Connect package is installed on your instance.

To resolve the issue:

1. Go to the EC2 dashboard in the AWS Management Console.
2. Select your EC2 instance.
3. Click on the "Security" tab in the instance details pane.
4. Find the associated security group and click on it to edit its rules.
5. Add a new inbound rule for SSH (port 22) with the source set to the EC2 Instance Connect IP range for your region. You can find these IP ranges by searching for "EC2_INSTANCE_CONNECT" in the AWS IP ranges JSON file.
6. Save the changes to the security group.

If you've verified all these settings and still can't connect, try rebooting your instance. If the problem persists, you may want to consider using alternative connection methods like AWS Systems Manager Session Manager or reach out to AWS support for more in-depth troubleshooting assistance.
Sources
EC2 instance failed to connet | AWS re:Post
EC2 Instance Connect cannot connect to my instance ! | AWS re:Post
AWS Instance Issue | AWS re:Post