Why was my rank not reset in a Fortnite game mode after the season ended?

The Battle Royale and Zero Build ranks reset whenever a season ends, however, other game modes may have other reset times. 

You can keep track of the rank reset dates by following the respective social media page:

• Fortnite (Battle Royale, Zero Build, Reload) - Fortnite (@Fortnite) / X (Opens in a new tab)
• Rocket Racing - Rocket Racing (@RocketRacing) / X (Opens in a new tab)