You need to check this tree items:
1) Jot Port may be closed for external connect, you may check it with command from command line:
telnet mydomain.org YOUR_PORT
2) Jot Server app is not running on your server. You may check it with this command via SSH access on the same server where Jot Server is installed:
ps ax | grep app.js
and if there is no node app.js process in the results list, it means that Jot Server is not running.
3) Certificate problem: namely there are wrong paths to certificate files in Jot Server's config/config.json file where were defined or defined certificate is expired.