Lizzie, you need to get in touch with them because everything that's been written has said if you have an annual subscription, you should get the discount. I'm sure it'll be a pain in the whatnot but you're not going to get it otherwise
I've just looked at my account setup and seen there's a button for "Receive occasional newsletters". Maybe that's been turned off on yours?
For the latest email, your hypothesis is not the reason, as I haven't unlocked any records from my account and I still got the email