"I cannot connect to my ssh server" is a common new-user issue. Most commonly it means that either the new user misread the how-to-set-up-ssh instructions, or that the new user is perhaps a bit weak on their networking skills. We all had to learn sometime.

1. Simplify to make troubleshooting easier: Put your ssh client and ssh server on the same network. This is how you troubleshoot problems with account names, passwords, keys, and firewalls.

   
   

   Um, remember that your ssh server needs a consistent IP address. There are a couple ways to accomplish that. Double check that the server's IP address is still what you thought it was.

   
   



2. Once you have successful key-based ssh login on your client on the local network (LAN), then your Ubuntu server is configured correctly. Make no further changes.

   
   



3. If you can connect from the LAN, but not from the wider internet, then DON'T look to your Server.

   
   
   
   
   • Look at your router -- did you remember to set up port forwarding? If so, remember that you must use the router's IP address if connecting from the wider internet.
   
   
   • Is your router's firewall blocking your SSH port?
   
   
   • Some ISPs block port 22. Does yours? If they do, try a different port. (That means change your port-forwarding on your router, NOT your server).
   
   
   
   



4. The actual error message is important! An error of "invalid key" or "no such account" means to go back to step 1. An error of "cannot connect" means a network issue -- typically you are using the wrong IP address. Copy/paste the error message into your favorite Search Engine.