A4 Mk1 & Reaper, recording fine but no DAW output via headphones

Just setting up the A4 with Overbridge and Reaper on my laptop. Is using the A4Mk1 as an audio/ASIO interface using the headphone jack supported?

It’s recording fine (set up the ASIO inputs/outputs in Reaper to A4 main outs) but it’s not playing the Reaper output through the headphones. Routing looks fine and showing an output signal in the mixer, but the headphones only play the A4’s internal sounds.