It is indeed three years of inactivity.
Some of these threads may provide some ideas:-
If you see references to qualifying for Reward Flight Saver, it's fundamentally the same issue as yours: you need to earn at least 1 Avios in the past year to qualify for RFS, and earning 1 Avios in your account will also keep it alive for 3 further years (and ditto for your wife's account).
Last edited by Globaliser; Mar 17, 2021 at 12:10 am
Reason: So that thread titles will show in the links