On the Redline HMI, when using some webcams , the can require more power than the HMI can produce in the usb ports, and may result in no video, or the touch screen ‘touch’ being ‘off’ from where your finger touches or you have more usb devices than the two empty usb ports on the side of the hmi, a hub will offer more ports.
These will require a powered usb hub.
This is the one we recommend: Amazon.com: SABRENT 4 Port USB 3.0 Hub with Individual LED Lit Power Switches, Includes 5V/2.5A Power Adapter (HB-UMP3) : Electronics