You need to go one more screen before entering the code. Order, proceed to checkout, enter in all your info including red card number and address, press to next screen. On the final page you enter the two promo codes. Took me several leaps of faith to get there, but it works. My total after 6% state tax is $220.23. Order is processed and ready to ship.
I think the deal was either an error, or it's been overused and they killed it.
Earlier I was able to stack both codes with no problem, but I cannot replicate it now and it's giving me the same error messages as the others are getting about the offer not starting.