A "blinking" tracker is usually the result of a lack of sufficient power. If you have multiple USB ports where you can attach your Tobii 4c, try moving it to different locations. Having the tracker plugged into the opposite side of the computer from the external monitor often solves the problem. If this is not possible, or doesn't work, try adding a powered hub. A powered hub plugs into the wall and connects your devices to your computer. You can purchase a powered hub any place you normally purchase computer accessories. Be sure it is POWERED. This means it must plug into the wall. The extra power is what solves this problem. Here is a video showing you how to attach it.