The tech at the West Covina Latus dealer told me the Toyota compressor is exactly the same and about a 1/3 the price ($400) of the Lotus one.
How did you check that the flap was working without taking the clam off?
You have to remove the 2 top grills, then disconnect the big rubber duct and push it to the side. Shine a flashlight down the hole and have someone switch the climate control from cold to hot and vice versa. You'll see the flap move back and forth. If it doesn't, then your flap is either stuck or something more serious.