Final answer:
The monitor connected with a USB-C cable may not work if the computer's USB-C port or the cable does not support DisplayPort alternate mode or is not Thunderbolt compatible. The listed cable types are not directly relevant to the issue; compatibility between the port, cable, and monitor's signal requirements is key.
Step-by-step explanation:
If a support technician plugged a monitor with a USB-C cable into a USB-C port on the computer and the monitor would not function, there could be several reasons for this issue. It's important to note that while USB-C is a type of connector capable of transmitting various types of data, simply having a USB-C connector does not guarantee display compatibility. USB-C ports can support different protocols, such as USB data transfer alone, DisplayPort, or Thunderbolt.
For the monitor to function properly via USB-C, both the computer's USB-C port and the cable must support DisplayPort alternate mode or be Thunderbolt compatible if required by the monitor. If the USB-C port on the computer is not designed to carry a video signal or if the cable is for USB data transfer only and not meant for displays, the monitor will not receive the necessary video signal. Therefore, without the proper support for video transmission, none of the listed cable types (HDMI, DisplayPort, Lightning, or Thunderbolt) would be at fault in this scenario.
To resolve the issue, one would need to ensure that both the USB-C port and the cable support display output, and that the monitor itself is compatible with the transmitted signal. If these conditions are not met, using an appropriate adapter or a different cable that matches the monitor's requirements would be necessary.