Video issues get complex fairly quickly, but there are several things you can check and/or try:
Double-check your 'source' choice on the touch screen:
Some rooms may have more than one cable choice or another source choice may have been inadvertently touched.
Is the 'Hide Image' button active?
It looks like this when it is: 
or like this: 
Switch the adapter:
Some rooms may have more than one USB-C to HDMI adapter provided. Additionally, if you have a Carleton-provided laptop, you were also issued a USB-C hub. Please try one or both of those options. OS and hardware updates to BYO devices can play havoc with adapter interoperability.
Didn't find what you needed? - Submit a classroom issue ticket or call Classroom Support at x5002