Diagnosis
This monitor does not support Power Delivery (PD) over its USB-C port. The USB-C port is for video and data only, so it won't charge your laptop.
How to Fix It
You'll need to keep your MacBook's original power adapter plugged in separately. Use the USB-C cable to connect your MacBook to the monitor's USB-C port for the display signal. Your laptop will need to draw power from its own charger.
If That Didn't Work
If the screen isn't displaying at all over USB-C, check your MacBook's display settings. You might need to manually detect displays. Also, ensure the monitor input is set to USB-C. Press the joystick, and if needed, use the Input button to switch to the USB-C source.
Heads Up
The USB-C port on this monitor is handy for a single-cable connection to phones or tablets that support video-out, but for laptops, remember it's video-only. Don't rely on it to power your device.