If your external monitor is not working with the USB-C to USB-C Gen 2 Flat Cable, the most likely cause is a USB-C port that does not carry video. The USB-C port on your host device must support DisplayPort over Alt Mode (DP Alt Mode) for the USB-C to USB-C Gen 2 Flat Cable to output video, and the cable supports a single display at up to 4K and 60Hz.

How to fix display problems with the USB-C to USB-C Gen 2 Flat Cable

1. Confirm your host device's USB-C port supports DisplayPort over Alt Mode (DP Alt Mode). Without DP Alt Mode on that port, no USB-C cable will send video.
2. Reseat both ends of the cable, in the host device and in the monitor.
3. Try a different USB-C or Thunderbolt port on your host device. The cable is compatible with Thunderbolt 4, Thunderbolt 3, USB4, USB 3.2, USB 3.1, USB 3.0, and USB 2.0 Type-C ports, but not every port on a computer carries video.
4. Connect the other end to a USB-C or Thunderbolt input on your external monitor, then switch the monitor to that input.
5. Detect the display on your computer. On a Mac, open System Settings and go to Displays. On Windows, open Settings, go to System, then Display, and select Detect.
6. Set the right expectation on resolution. The cable supports a single display at up to 4K and 60Hz.
7. Test the same monitor with another cable, or the USB-C to USB-C Gen 2 Flat Cable with another monitor, to work out whether the cable, the host, or the monitor is the problem.
8. Check the connectors on both ends for debris or bent pins.
9. If you are charging through the cable and the device charges slowly, check what your host supports. The cable carries charging up to 240W, but not all host devices support 240W charging.
10. Do not use the cable in place of a Thunderbolt 3 cable. The USB-C to USB-C Gen 2 Flat Cable does not meet Thunderbolt 3 data speeds, so a device that requires a true Thunderbolt 3 cable will not work as expected.