This usually means the wrong topology page is open, or the "Run" button has not been clicked. Close the current topology page, and go to File->New and open a fresh page. Click OK on the opening initialization page. Then click the "Run" button (the little green running man at the top). A green/red/yellow status button appears in the lower right-hand corner of your screen. The respective RT icon should light-up (green/yellow/red) according to its status.
Other analyzers may have a default activity page that is always on. With our product you must open the appropriate topology page and activate it. This allows greater flexibility and capability, but does require another step.