Yep, we have the same problem.
Note in your small print you posted:
Offer excludes categories 1A/4S/5A/6E/7A/8P/8S/9A/IS/OV/BL/SS/ST/11/12
We have a 1A guarantee booked and 1A specific cabins booked and for most of these you have to pay for at least a 4A as the above posted noted.
I know rats!!!!