This article discusses why some devices may not support video over USB-C

Not all computers equipped with USB-C has the ability to deliver Video. It is up to the individual computer manufacturer as to whether they incorporate Video through the USB-C port. This is sometimes referred to as "USB-C DP Alt Mode" or "DisplayPort Mode." This is what allows video and audio over USB-C. 

For example; On an HP ProBook x360 11 G5 EE computer, the specs on the HP's website indicates: (1) USB Type-C connector (Data transfer, Power Delivery)
On the above pc, you would be able to power an Elo USB-C equipped monitor and get touches on the touchscreen but you would not have any video. Video would only be possible by connecting through the HDMI port and not the USB-C port.

Some computer manufacturers require changes in the BIOS before the USB-C port is capable of delivering video. Check with your computer manufacturer for help with this.