Tax GEOCODE Generation from AR Invoice

Hello,

I am wondering if someone can tell me how the GEOCODE is being generated when creating a manual invoice within Oracle AR?  I would think it should look at hz_locations first, then...go somewhere else based upon the City, County, State and Zip to generate the GEOCODE.  I can't seem to figure this out.  We are getting a Vertex Error.  However, if i modify the address to my city, county, state and zip it goes thru without error.  I'm guessing that there is something invalid setup with the other one but i don't know what it could be.  Any assistance would