I've done it a couple of times in the last few months and it has gone as smoothly as glass. The electronic PMUs are deducted from the account, the itinerary on delta.com immediately reads "Business" and "D" class and shortly thereafter the reissued receipt arrives in my e-mail box.

But I do not fool around with any delaying as the OP is doing. I book with an agent when I know that the Zs are there and although the first receipt may read coach, all the rest falls into place very quickly.