Classes on an Accountant's Copy

I have a client who uses classes.  I used to be able to apply classes to the entries I made while I had the Accountant's Copy.  Now, it is grayed out and won't let me apply classes to some of my entries. I can do it on checks, and journal entries, but it won't let me use classes on invoices, credit memos, bills.  I called QuickBooks and they basically thought I was crazy and they had no answer for me. 

The field for classes is orange or peach, however you look at it, so it should be a field that I can use.  I just don't know why this is happening and it's like this with all three of their company files.  Thanks!