If you're experiencing the HDMI port not working, please check into one of the following things below:
1.) Make sure the cable connection setup is correctly. Rear USB-C port is for the USBC power adapter and the side USB-C port is connecting to computer.
2.) The length of the HDMI cable can not exceed 2 meters.
3.) Some manufactures make its cable that one end has to be connected to a display monitor, and the other end is connected to the source. Normally, the end to display monitor has a "TV" marked on it.
4.) user has to connect to a HDMI display monitor. It is not compatible with the DVI/ Display port or other non-HDMI monitor, even with an adapter.
5.) If none of the port on the hub is working, then please replace the USB-C cable that connecting the hub to computer.