The best way to set this up is to pair using ANT+ and not BLE. One side of the system is the controller. Typically the left side. You only need to pair to that side. It then communicates to the other side and aggregates the data and sends it back to the head unit.
Check that the left and right sides are paired together. You may need to use the vendors app for that then over ANT, where you should only see the one sensor.
