Be sure you can ping the supervisor, using the operating system's ping command-line utility. If you cannot, there is a networking issue outside of Qube.
Check firewall settings. We prefer that machine-level firewalls are disabled. If you cannot turn off the firewall, open ports 50001-5002, 50010-50012
Be sure qb_supervisor is set to your supervisor's hostname or IP address in the local machine's qb.conf.
Be sure qb_domain is consistent across your facility. The default and recommended value is "qube" (note: This is the qube domain. It not related to any other domains in your facility)