UR12 With Monitors and Headphones at the same time

I have a UR12 connected to a pair of monitors via RCA. I’m trying to have my headphones plugged into the headphones jack and be able to switch from headphones to monitors easily while recording. Is there a way to do this?

When I plug my headphones in, nothing happens. Sound is still coming from the monitors only!

Using Macbook pro and Fl Studio