This is VERY important to do at the onset of a new season. Updating your account season (as well as the active season(s) of your new and returning athletes) is the key to setting which players are available to be tagged in this season's games, and which ones will show in the current season's stats. Also, only current, active-season players show when creating Reviews.
You can check your season setting in your SETTINGS, under the 'Seasons' tab. Simply choose the correct season from the dropdown menu:
The system will automatically update the context of your account to the selected season.
Equally important is to set the proper 'active season' for your athletes. For more information on that, please see this article here.