I am new to Openx and not finding the appropriate documentation of Openx 2.6, which we are using. I just want to be able to target by US/Canada Postal codes. There is a plugin for "geo targeting" which is already added and installed in our project and many geo targeting options are appearing in the dropdown. See the pic -

But, only the US/Canada postal code option (or may be some more) is not appearing.
Also, above is the case of one of our servers where the app is installed. In another server, US/Canada postal code targeting option is appearing fine.
Now, I guess there is some proper way to configure this to display, instead of finding in code, what is the difference. At least, send me link to the proper documentation please.
Thanks.
Also, could somebody please add a tag for Openx?