Actually, when the promo started, there was no coupon code, and then it was revised, and a coupon code was added.

Presumably if you have a printout of the promo from the time when it had no coupon code, and it had an expiration date before which you rental occurred, you should be able to fight it, but it might take some fight. I'd say Avis is probably unaware at this point that the promo originally didn't need a coupon code, because they updated their systems to the new version of the promo that does need the coupon code.

AWDs and coupon codes serve two completely different functions usually. The AWD is for discounts, the coupon is for bonuses.

It therefore should not be sufficient to put in just the AWD. The early version of this promo was the exception, not the rule, and it was presumably because of confusion it caused (for Avis, if no one else) that it was revised to use a coupon code.

In my case, I used it without a coupon in mid-October and got my 5x (it showed "5" on my rental receipt correctly, but it didn't all post at first, but since it showed it on the rental receipt they corrected it after I called). I then used it again at Christmastime and took care to enter the coupon (since I'd seen elsewhere on FlyerTalk -- probably in the master car promo thread in MilesBuzz! -- that there was now a coupon) and got my 4x (didn't do enough days for 5x) and that all posted over to WN automatically.

(The Avis rental receipt shows the count of 0.5 credits you earned, so normal earning shows as "1", 4x shows as "4", 5x shows as "5", etc. Take the number they show and divide by 2 to get the actual number of RR credits the receipt says you earned, so "1" means 0.5 credits and "5" means 2.5 credits.)