You can only use Extended Mode or Copy Mode if your computer supports dual or multiple monitors.
If you need to output to two monitors and share the USB device, each computer's USB port and two DP output ports need to be connected to the USB C port and two DP input ports of the device at the same time.
If the USB C input port of the product is not connected or is connected incorrectly, the USB device connected to the output port of the product will not be recognised.