I did have a subscribe and save order the other day; the $10 was not applied.Have you set up any subscribe and save? I did and it ships the 15th. I also ordered a new firestick the same day that the $10 didn't come off. I couldn't find it and finally looked at the s&s and that's where it had applied. So crazy.
I chatted with amazon yesterday. It has to be a product sold and shipped by amazon. The credit does not expire, so eventually I will order something that qualifies.