Try these steps:

• Try a different USB-C to HDMI or USB-C to DisplayPort cable on the hub's USB-C data and video port.
• On Mac, go to System Settings > Displays and click "Detect Displays" while holding the Option key.
• Connect the monitor directly to your computer to confirm the monitor works.
• Confirm your computer supports video over its USB-C port — not all USB-C ports carry video.

If the problem continues after these steps, submit a support request.