I received my LG 27 inch 5K monitor today and plugged in to the electrical outlet but the screen stays dark. My new macbook pro arrives in a couple of days as a separate shipment. Does the computer need to be hooked up to the monitor for the monitor to come to life? Also I notice of the four USB ports on the back of the monitor. One has a lightening bolt. Is this one suppose to be used for a specific purpose compared to the others. Unfortunately the monitor came with little to no written documents to answer these questions.