Can't get anything from the IEC 62056-21 Binding

Add-ons Bindings
1

I have been trying to get the IEC 62056-21 Binding working with a Landis+Gyr E470 meter. So far the only output from the binding is

2016-08-08 22:43:07.414 [DEBUG] [b.i.i.Iec6205621MeterActivator:34  ]- iec6205621meter binding has been started.
2016-08-08 22:43:07.796 [INFO ] [o.b.i.i.Iec6205621MeterBinding:208 ]- Created reader lecky with  IEC 62056-21Meter DeviceConfig [serialPort=/dev/ttyAMA0, initMessage=null, baudRateChangeDelay=0, echoHandling=false]!

I have -Dgnu.io.rxtx.SerialPorts=/dev/ttyAMA0 in the startup command and openhab is a member of the dialout group.
I have confirmed that I can talk to the meter using this handy script

$ python test_signon.py
/dev/ttyAMA0 opened successfully
>  / ? ! CR LF
<  / A M P 5 M 1 1   >>>   Data: 2f414d50354d3131 Length: 8
AMP : Ampy Automation Digilog Ltd
  5 : Baudrate changeover identification, rate = 9600bd
 ID : Meter identification string = M
>  SOH B 0 ETX q
/dev/ttyAMA0 closed successfully

…but this script will run whilst openhab is running, which I think suggests that openhab doesn’t have the port open.

So I’m now stuck. What can I do to trace what is happening (or not happening)

Thanks,
Mike.