TF LUNA LIDAR Sensor not working with Ardupilot 4.3.6 and Navio2

I have tried for many days to figure out, why Ardupilot 4.3.6 (latest fw) does not read the TF LUNA LIDAR Sensor.
I’m using an USB-TTL converter, and connecting it to one of the (Raspberry Pi 3b+Navio2 board) USB ports.
I know for a fact that the TF LUNA Sensor data comes into the Raspberry pi, since I used a simple python program to capture the data coming from the sensor into the ttyUSB port.
Yet, Mission Planner still produces a “Bad Lidar Health” message, and Sonar Range and Sonar Voltage display only zeros.
If anyone can provide any help or constructive suggestion, because I’m at my wit’s end on this one…

See configuration below,