Did you have to make the reservation after the promotion started?
I went to KOA two days after the promo started, so that reservation was made well before that.
By the way, I had not gotten any miles for my almost 3-week rental in KOA after 8-weeks, so I had to call them to put it through manually (even though my profile says that's what is supposed to happen), so when their allowed time period is up, get on the horn to them or it probably won't happen.