External camera not detected when connected to external monitor

Hello! I have two Macbook Pros.

This works for detecting an external camera:

• Macbook Pro 2018 ---(USB-C)--> external monitor ---(USB-A)--> external camera
• Macbook Pro Mid-2015 ---(USB-A)---> external camera

This doesn't:

• Macbook Pro Mid-2015 ---(HDMI)---> external monitor ---(USB-A)--> external camera

Is this expected behavior for older macbook models or am I just missing some configuration settings on one and not the other? Am I using the wrong cable for the Mid-2015?

Thanks in advance.