Port 22 Operation Timeout on an instance that YESTERDAY was working perfectly. I have changed nothing.

Question

Hello, I'm quite frustrated with the situation I'm facing.

Yesterday I had an EC2 instance set up for a Django application (python). I was able to SSH into it, made the necessary connections to the RDS, accessed the system through the public IP and DNS, and it was working perfectly.

This morning, I turned on my computer, tried to SSH to update git, and I'm getting a **Port 22: Operation Timeout.**

I have other instances in the same VPC that are working without any issues.

The rules, which I haven't modified, are as follows:
**Inbound:**
22	TCP	0.0.0.0/0
443	TCP	0.0.0.0/0
80	TCP	0.0.0.0/0
8000	TCP	0.0.0.0/0
**Outbound:**
All	All	0.0.0.0/0
(I have two more for the connection to the relevant RDS, but I understand they shouldn't be a problem because everything is open.)

I also can't access through EC2 Instance Connect.

I want to emphasize that since last night when I left everything working, I haven't changed absolutely anything, and nobody has updated anything. I've compared the rules and the data of the EC2 instance with the other instances that do work for me, and everything is the same.

Please, I need to fix this in order to progress with the development of my application.

I tried rebooting and stopping and starting the instance. The NACL that is the same of the other instances, is already well configured. The same happens with de VPC settings.

I can SSH everything except this instance. TODAY. Yesterday I was able...

Answer

Hello.

Is the public IP address of your EC2 instance the same as the one you used yesterday?  
The public IP address of an EC2 instance changes when you stop and restart it, unless you are using an Elastic IP address.  
https://repost.aws/knowledge-center/ec2-recover-ip-address

If you still cannot connect, please check the logs by following the steps in the document below.  
There may be some errors in the log.  
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-console.html#instance-console-console-output

Answer

What are the CloudWatch metrics for the EC2-Instance? Any abnormalities?

Having your port 22 inbound sec group open to 0.0.0.0/0 makes it vulnerable to botnets or other bad actors (even if it was a single day). For safety I would go ahead and terminate this machine now because the gates were already open. Create a new sec group to your IP address or to an SSH box and then create a new EC2-Instance with this security group.

Port 22 Operation Timeout on an instance that YESTERDAY was working perfectly. I have changed nothing.

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