Call to pd_getaddress returns ""

I have 20 boards in the field at 15 different locations. I need to retrieve the MAC address of the board at power up or firmware update so that certain variables can be set based on a boards location, ie MAC address.
I am using the following DC and board

DC 9.62
da30f3 - it MAC address
code :
unsigned char mac_buf[6];
_rk_pd_getaddress(0,mac_buf); // it does not matter if I use this line.
pd_getaddress(0,mac_buf); // or this line as both return “” as shown below

Evaluate Expression
mac_buf char * (0x9D3B) “”

I seem to be missing something fundamental but do not know what it is.
Any insites would be appreciated.

I use SysIDBlock.macAddr to get the MAC value.

Tim S.