Tournament Credits are reset at the end of each season.
Players who participated in Competitive Tournaments during a Season will be granted an All-Star Cup reward. Your Tournament Credits will convert to the highest level reward that you are capable of earning based on your Tournament Rank and Tournament Credit amount.
These reward items will be delivered during the start of the next season.
In order to receive these reward items, you need to log into Rocket League at least once at any point during the Season.