Purchasing Freight Calculation - How Does this Work?

Hi,

In a DEMO environment.

I am trying a very simple freight calculation to see how the Purchasing Freight Calculation works but nothing calculates.  I have done the following set up:

1.  Arbitration Plan - ship to location

2.  Rule Entry - specified ship to location and defined freight as Order Value and 12% with start and end dates

3. Create a PO and add the Arbitration plan

4.  The PO has the freight terms and ship via populated

Click on calculate or use the Go To link and select Freight Calculation and nothing is calculated

Am I missing something or does Pu chasing not calculate freight?.