DIAGNOSIS The monitor is receiving power but not a stable video signal. The most likely cause is insufficient power delivery through a single USB-C cable.
FIX You need to supply both power and video. Connect the monitor using two cables. First, connect the included USB-C to USB-A cable from the monitor's USB-C port to a power source like a laptop USB-A port or a phone charger block. Second, connect a separate USB-C to USB-C cable from the monitor's other USB-C port to your laptop's video-out/USB-C port. The monitor should power on and display.
IF THAT DIDN'T WORK Confirm your laptop's USB-C port supports DisplayPort Alt Mode. Try a different, high-quality USB-C to USB-C cable known to support video.
HEADS UP The monitor's USB-C ports have different functions. One is for power-only input, the other is for combined power/video input. Using the wrong one as your only connection will cause this black screen issue.