Heading info not being accepted/used

[Karanga]

I have a TMQ AP4 autopilot, which is working well. I want to use its magnetic heading info to assist in radar operations, plus other options within O5.

I have connected the nmea port and created a new connection. The nmea debug window shows that heading info is being received by O5, but it is not being utilised.

In comparison, a Bluetooth connection from my phone compass does get utilised and displays both magnetic and true heading.

So why is the AP heading being ignored?
The full sentence is
$APHDM, 133,M*08<0x0D><0x0A>

The 133 changes as the heading display on the AP changes

There is no HDG or HDG message received from the autopilot.

Any suggestions will be gratefully received.

Tim