I have installed the following module on 1.3.6 (the site just went live a few weeks ago)

Stock by Attributes
Version: 4.3.1
Zen Cart™ Version: v1.3.6

But when someone makes a purchase it does not deduct from the inventory level.

I am not even sure where to start looking to fix this problem at this point.

Has anyone had this same issue?

Thanks in advance for your help.