Magazine Subscription redemption code not useable/valid

I used some of my rewards points (account is Jtroxel1@yahoo.com) to order two magazine subscriptions: Forbes and Popular Mechanics. The Forbes subscription proceeded without any issues; however, when I used the code I received for my second order, Popular Mechanics, the MyCokeRewards magazine subscription center tells me that my code is not valid as of today, to check if my code has expired. I copied and pasted the code; i tried multiple times; I cannot find anywhere to verify if my code is valid, but I did save my reward instructions. Please tell me how to proceed. Thank you, Jason Troxel