Under your account details online, is your email and home address correct?
Do you have the Fly Buys mobile app? For me, the paper voucher offers have been replaced by offers via email and in the app.
At the bottom of your account details, have you filled out information in this section:
For a better experience with flybuys, tell us a little bit more about...
(Up to you how accurate you are with providing the specifics, but if you say you don't drink alcohol, then you probably won't get any Liqourland or First Choice offers).
In your account online, have you looked at your card details, and the option to Manage your communication preferences? Actually, that is probably the first area you should try (I've been "writing out loud" as I think and click through my FlyBuys account. You'll see options like this:
I suspect all of yours may be not ticked? It's either the communications offers are blocked or there is some problem contacting you, such as typo in email or old home address, I would guess.