There was an error when modifying a ItemInventory list, element " *** ". QuickBooks error message: The COGS account cannot be changed.

You have to edit the failing products in QuickBooks and make sure that the same COGS account is specified in AdvancePro. The COGS account can only be changed on an Inventory Item which has been used in transactions from within QuickBooks, so if it is different in QuickBooks, they need to change it to the same account that is specified under AdvancePro`s Account Name for COGS" from within the QuickBooks User Interface.