You need to check this tree items:
1) Port number 5000 may be closed for external connect, you may check it with command from command line:
telnet mydomain.org 5000
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 were defined or defined certificate file is expired.