If you currently have a card in your lineup, any additional versions of that player will not be presented to you as a selectable option.
For example, if Rookie Jeter is in your lineup, you will not see Cover Athlete Jeter as an option. You are unable to have Two Jeter cards in the same lineup, even if they are different series. To view and add a different version of the same player card, you'll need to remove the card that is already active on your squad completely from your lineup and bench.