Amazon instance can't connect after 23days

More of a suggestion for future usage, take a look at the Systems Manager session manager, in case you're not able to SSH it will help with access easier than EC2 instance connect in my experience: https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager.html

What @Brettski@AWS mentioned is also what I'd recommend for troubleshooting it could be that the system is just in a hung state and a reboot from the console will resolve the connection issues. You can take a look at the CloudWatch metrics as well to see if perhaps you hit high CPU and that's why the machines has issues.

I have the same problem but no joy with reboot :'( I think it's an authorization problem because I faced the awful "sudo must be owned by uid 0" error message after trying to update my servers SSL's and then reinstated mistakenly typing "chown root:root /etc" (instead of /etc/sslSubfolder...)... So now I can't access this instance (and this instance only) neither over SSH nor over the web based EC2IC. Serial connection is not possible due to incompatible instance type. The consequence is that I can't fix the authorization cmd mistake I made since every troubleshouting doc I see involves connecting over SSH... I can't even restart the SSH service on this instance. Restarting the instance didn't change anything. Even hard restart which may also have caused more issues although using elastic ip's so records are intact but apache config seems altered too.