If I had to guess, I'd think that OP put in a lot of entries into the September Sweepstakes for this item (found here:
https://1.shortstack.com/8DzfMr), but from what I can tell those sweepstakes are over.
If he has large quantities of codes my guess is that more than likely they figured out a way to hack the code progression like with the Google Home deal. Note that from the link you posted NY and FL residents are excluded and I think the OP mentioned only 1 per ADDRESS. They are being sold on eBay from $49 new and up.
Huh, I thought the Google home deal was just many entries. One guy was selling echo dot codes that were from a siriusxm event, and there's no way he cracked those because they were all randomized. The main reason I'm guessing this is a bunch of entries is because the entry form for the promotion has 0 verification that you are not a robot. No Captcha, no cookies preventing you from entering multiple times, etc. 1 per address makes sense because I'd imagine you're supposed to be limited to 1 per person/email. Maybe I'm being too optimistic. Hopefully I didn't buy cracked codes -- once I saw that sweepstakes submission page I just assumed it was a set of spammed entries.