can you check in the "Account" tab that your subscription is still running? Each picture for an "active" expansion (the ones you have access to) should be in color, all others in greyscale. In addition, under each expansion picture is the end date (past or future).
If that really checks out and your subscription is still active, did you change any parameters for the search recently? Best chances for matches are if your search includes "2P" (2 player games) and "rated" (rated games) and the values at "min rating" and "max rating" are not near zero (-10/10 should be good enough).