There are not enough GUI/Render node licenses on the license server. Each machine that wants to use V-Ray inside a host platform (3ds Max, Sketchup, Rhino, etc.) requires 1 GUI and 1 Render node license. Please make sure that no other machine is currently engaging your V-Ray licenses. You can see which machine is using V-Ray on the Chaos license server page (http://localhost:30304)