You would think that wouldn't you?
I don't know if the @Gamer coupons are different for some reason, but I have never been able to get a Best Buy employee to honor my Reward Zone coupons or gift certificates when I've pulled them up on my phone.
In their defense every time this has happened they have given me access to a computer to log into my email and print out the coupon and then accept it, with only one exception. But I have never been able to get them to take any coupon digitally.
So I guess I am wondering if you have to download a special app or something for this to work? I always just pulled the link up on my phone through my email or my Best Buy member's page.
Your store needs to freshen up on policies then. MyRewardZone has it detailed more in their terms for certs.