The thing I found with the code was odd.
I did a lot of transactions with debit card, but the card expired and the new one didn't arrive. (I finally got a replacement much later, after a 5-week transit time from USA to AR, but that's a different story.)
Anyhow, when I changed from using debit card to pulling directly from checking account, and tried to use the code, the transaction was stuck in limbo forever. I deleted it and tried again, with same result. Finally, I deleted the second attempt, and made a third without the code, and that went right through, albeit with a 4-day delay. I mean, the transaction was approved, but it said I couldn't pick up the money for four days, as opposed to the first two which just said pending approval or something like that.
Then, after having paid the fee once, all subsequent transactions directly from checking account not only accepted the code, but were available for immediate pickup, without the wait.
It was like they insisted I had to pay the fee once from a new source of funds, before I could use the promo code.
As always, YMMV, your mileage may vary. WU is not always consistent. We have established earlier in this thread that some of us are charged higher fees than others, (absent the code), even when all factors seem to be the same.