Diag/ system not heating. Found outdoor unit not running due to L2 error code, HPCO (3 trips). Reset system and checked pressures and they are ok, evap coil is good and filter was just changed, tested dampers and they are opening and closing properly. Inspected ductwork to see if there’s anything that could be restricting airflow and found the bypass damper was stuck partially closed. This bypass allows “extra†air back to the return when less zones are calling to help prevent high pressure build-up. Was able to loosen it up for now, used a strap to hold it partially open to help. We will see how this does, system is heating properly at this time.