Many LeapTV games feature auto-adjusting curriculum. With this feature, the questions your child is asked become more or less challenging based upon on how many of the previous questions were answered correctly.
If you feel the questions being asked of your child are not challenging enough, the difficulty of the questions will automatically become more difficult as your child answers more questions correctly.
Sometimes a parent or sibling will play for a period of time under a child's profile, inadvertently leveling up the curriculum enough that the questions become too challenging for the child. While answering these more difficult questions incorrectly will eventually level down the curriculum to an appropriate difficulty for your child, to immediately address the issue, you will need to delete the existing player profile and create a brand new one. Note, if you regularly have one than one person playing, you should set up separate profiles for each player, or ensure other players always sign in using the "Guest" profile.