AX2012 Retail POS Weigh Scale "Place the Item on the scale" message

I am setting up a weigh-scale to AX2012 Enterprise POS.  
I have the Register and weighed-items correctly configured and have installed the CCO OPOS drivers Vers. 1.3 and the OPOS driver from the manufacturer.  The scale works fine from the OPOS test program and can read the weight correctly.

In AX POS, when I scan a weighed item, I get the following message at the POS:

"Place the item on the scale." I have 5kg on the scale!

The POS is communicating to the scale, for instance if the scale is showing below zero, the POS does not respond, or if the weight has not changed, likewise, it requires the weight to be changed before the message appears.

Message:

Any tips or advice would be great

Thanks, Tony