3-Coupon Giveaway: -75% Trine (x1), -75% Trine 2 (x2)

"Can't be applied with other discounts" is exactly what I meant when guessing that "discounts at Steam won't stack". If the coupon isn't being accepted now, it could be because the game is currently on sale. Hopefully the coupon will work once the sale ends, so give it a try then. If for some reason it still doesn't work then, maybe you can contact Steam support and get some help with it. If they ask where it's from, you won it on the Summer Seal giveaway Frozenbyte was doing. :) (Frozenbyte might be able to help, too, if necessary.)

Yes, I think so. If you enter too many invalid or duplicate keys that can happen. I think it can also happen if you enter a whole lot of valid keys quickly. I think it's some kind of security/safety measure on Steam's end, though I personally haven't read a detailed explanation of why they do this. The block should last for maybe an hour, so you should be able to enter keys again then.

Thanks for the info. I'm going to assume that means the two Trine 2 coupons I posted are taken then. It would be nice if people would say when they get keys, especially since I explicitly asked them to, but oh well. Good luck. BTW, doesn't the collector's edition have more content than the regular one? Why do you want the regular version instead? Just curious.