When you see the render slave in the Coordinator than usually it should work and the computer can see each other and everything is setup correct.
It might be a different problem you are running into. The complexity of your scene. On the screenshot it looks like it doesn´t even use all cpus on your local machine. swarm rendering distributes each lightmap to a virtual cpu. So if you have less lightmaps than cpus it´s won´t distribute. As unreal merges some lightmaps you might even have less lightmaps than you would expect. In the swarm agent of your local machine, “developer settings” set LocalJobsDefaultProcessorCount down to something like 4, to limit the accesible cpus on your local machine wich might force the swarmer to distribute the maps over the network.