mopani

I'm running Helix edit with Helix lt to reaper. MacBook Air M4 running Sequoia 15.3.2. All settings are double and treble checked, latest drivers installed etc etc. and Reaper simply won't record from Helix. I can play back audio from Reaper through Helix fine but it won't record. Any help much appreciated because this is a new one for me. It might be something simple, don't know. Thank you.