Resilio Connect Agents use Tracker server as one of the means to discover each other. Each agent in a job connected to the tracker server configured in its Profile so as to communicate its own public and local IP addresses as well as discover other agents in the job.
The error appears only in cases when "Use tracker" option is set to "Yes" but the Agent was not able to connect to the tracker on the given address.
By default, the Management Console has a tracker server installed on the same computer. So the default tracker address for other agents will be the same as the address of Management Console, listening port 3000. In a profile that will look like this:
In this case, check that the tracker process is actually running. That will be Resilio Connect Tracker service in Services for Windows; or that there's
tracker a process running from the same directory as Management Console process for Linux.
Otherwise, there might be a custom tracker server installed and running. Check Profile settings and verify that the IP address of the tracker is correct and there're basically no typos.
If in either case tracker process is up and running and the address is correct, check the network tunnel itself, whether it is possible at all.
The simplest way is to use
telnet IP port command