Unable to connect to EC2 Instance

First up, make sure that SSH traffic is allowed in your security group. You'll want to check the settings there to ensure that SSH connections are permitted. If it's not, you won't be able to connect.

Next, let's double-check that your instance is in the right subnet and that the subnet has internet connectivity. If your instance is in a subnet that doesn't have internet access, you won't be able to connect remotely.

Another thing to do is to allow EC2 Instance Connect IP ranges in your security group. This is important, especially if you're using EC2 Instance Connect to connect to your instance. Without allowing these IP ranges, the connection might not go through.

If you're still having trouble connecting, it's worth trying alternative connection methods. Sometimes, SSH connections can be finicky, so using something like Session Manager might help narrow down where the issue lies.

When you're attempting to connect via SSH, keep an eye out for any error messages. They can often provide clues as to what's going wrong. It might be something simple like a mistyped command or something more complex like a network issue.

Next, make sure to check your instance's status and connectivity. If the instance isn't running properly or doesn't have the right network settings, that could be causing the connection problem.

And finally, if you've tried all these steps and you're still scratching your head, it's time to reach out to AWS support. Provide them with as much detail as possible about what you've tried and any error messages you've encountered. They'll be able to dig deeper into the issue and hopefully get you back up and running in no time.