Just to be clear-- so when you click on the pulldown next to Source Name, there are no entries in the list? It won't just show up there, you have to choose it.
But yes, if you are running your network on a switch that only supports 100Mbps you could be saturating your network, I suppose. But if the stream is viewable on a 2nd computer using the Studio Monitor program then you should be able to see it in OBS as well.