We have a Visio M43-C1 4K tv that will connect easily with several laptops, however when we use our Lenovo Y510P laptop, it won't display anything (using HDMI). The Lenovo has a GForce GT 750M graphics, and a native resolution of 1366x768, running WIndows 10. We have tried multiple resolutions, HDMI ports/cables. The laptop also connects to another TV (Toshiba), and to an external monitor. When we plug it in the TV is blank except for it states HDMI at the top, and flashes "2160p". I presume the laptop isn't displaying 2160p, so I think there's something wrong in the communication between the two. I've run out of places to look - any ideas are appreciated.