One of our developers forgot to add port 22 into allow list of firewall (Ubuntu Ufw). There are 2 way to resolve this problem:
- If you still have user/password of that VM, connect to the VM via Serial Port then login to open ssh port again.
- If you don't have user/password (My case), add a Startup Script to that VM then restart it. Start up script responsible is open port when the VM starts.
Then ... You have your VM back, Cheer!