C++ Boost Program Options - Command-line AND Config option unrecognised

I am trying to have an option be configurable via command-line and config file.

sample.ini
currency=USD

command-line
--currency

But I cannot seem to successfully configure the program options interface to read the currency in through the file.

Paste bin for code source: http://ift.tt/1ESGuMh

The output from above code:

root$ ./a.out add
Parse Error: unrecognised option 'currency'

Not sure what I am doing wrong, I look at a lot of examples and see the same code. All I can think of is that I use allowunrecognised which may interfere?