Recently there has been an extra step before being able to buy miles - there is a pop-up screen asking you to re-enter you name and USDM number (even if you are already logged in to your account).

I'm pretty sure this step determines if you have been selected for any current promotion.

Last round (August) I read about it on FT before getting an email notification from USDM, but was eligible after entering in my details via the pop-up screen.

For this current promo - I get no 100% after entering my details.