DIAGNOSIS The monitor is getting power but the backlight isn't activating. This is almost always a cable or power delivery issue, not a dead screen.
FIX First, check your USB-C cable. This monitor needs a cable that supports both video and power delivery (often labeled as "USB-C 3.1 Gen 2" or "Thunderbolt 3"). Swap in a known-good, high-quality cable. If you're using the included HDMI adapter, make sure the USB-C power cable is plugged into the monitor's other port and into a proper power source (like a wall adapter, not a low-power laptop port).
IF THAT DIDN'T WORK Try a hard reset. Unplug all cables from the monitor, hold the power button down for 10-15 seconds, then reconnect everything. This can clear a weird power state.
HEADS UP If you're connecting to a laptop, some need you to manually enable the external display via your OS display settings (Windows Key + P, or Mac Display settings). The black screen might mean it's connected but not set to mirror or extend.