Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Alamo won't accept Costco coupons

I was checking Alamo.com to see if my 7/12-7/20/08 OGG SUV rental has dropped in price. I entered the Costco corporate id and several of their coupons.

Despite the fact that I qualified for the coupon (e.g. the expiration date was 12/31/08, the car was an SUV as indicated, it was more than the 5 day minimum) it said that it could not be applied to the reservation.

I've never come across this before. Has anyone else had this issue?

I just used a costco.com coupon last week for an SUV in TYS with no issues.

There are limits to how many coupons they take of certain types of coupons, that could be it...or there could be "blackout" dates in effect...meaning events going on it town that has their coupons shut off. There are many reasons coupons don't go in. Read that small print, it's a laundry list of things that can make coupons not work.