Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Keep getting error message!

I don't know what I'm doing wrong. No matter what discount code I put in (TV, or any other, even leaving it BLANK!) I get the message " Rate sold out-Please try another or no rate code". I've tried several different rental locations. The only way I can get anything to come up is to change my country of residence from Canada to U.S.

Anyone have any ideas?