Reaktor is probably the deepest and most challenging vst's out there, due to the wide array of thing that can be built with it. In standalone Reaktor, you need to press the start playback button (top middle of the screen, left of tempo) to get Blue Matrix to play. All of the Sequenced Instruments and Groove Boxes work this way. Some instruments need to be played with a keyboard, and others like Metaphysical function, and the other Sound Generators, drone on and on forever, as intended. Reading the manual will help, also try utube for an introduction to Reaktor. Be patient, it will take a while to get the hang of it.