Vertex Integration for sales tax for City of Glendale, AZ

My client sells items to a customer in Glendale, AZ.  They have a TPT-2 (Transaction Privilege, Use, and Severance Tax Return) for Arizona that shows 2 lines for Glendale.  This is because there is 2 tiers for this tax, one at 2.9%, and one for 2.2%.  The 2.2% tax is to be paid if there is any one item on the invoice with a price greater than $5,000.00.  In any event, the city tax for Glendale is accounted for on this tax return. 

The problem is that the city tax for Glendale was not added to the invoice.  The invoice has the other taxes to be paid for this Geo Code, which amounts to 6.3%.  The client says that their business partner (a CPA firm) has reviewed all the Vertex setup,and that it's correct.  The CPA firm says that the problem is on the JDE side.  I'm guessing that the problem may be related to the fact that the determination of what qualifies for the 2.2% rate, versus the 2.9% rate is 1) systematically difficult to make in the system, and/or 2) difficult