Forms :: How To Get Third Combobox To Display Its Contents

I have a requirement that will need three cascading combo boxes - the second box should only display the contents that match or are relevant to the first combo box, etc.The title of the YouTube video is:

Microsoft Access pt 9 (Cascade Combo Box)

It seems the first and second combo boxes cascade and works fine. However, the third combo box remains blank after the second combobox selection has been made.

I have three tables: Customer, CustomerSubOrg, and PORs. I have setup lookup fields that are using Primary keys for two of the tables (CustomerSubOrg and PORs). However, I ensured that the primary key fields display as the "Names" of each instead of the numbers. I also ensured I went back and changed their data type to "Text" instead of "Number" so the text appears (which seems to have worked for box #2).

How to get the third combobox to display its contents? I've attached some additional screen shots below. I know the problem is within the second combobox -- perhaps the query needs some adjustment?Unfortunately I cannot attach images yet since I am now. But I basically created two queries and used them each for the second and third combobox.The comboboxes on the form:

Customer
Sub Organization
POR

The Suborg query looks like this:

Table: CustomerSubOrg
First Column:
From field SubOrg
From table CustomerSubOrg

Second Column:
From field CustomerID
From table CustomerSubOrg
Criteria [Forms]![frmMain]![cboCustomer]

The POR query looks like this:

Table: PORs

First Column:
From field PORName
From table PORs

Second Column:
From field SubOrgID
From table PORs
Criteria: [Forms]![frmMain]![cboSubOrganization]

Why wont the contents from the third combobox appear?