Rocket League save files can become corrupt over time and cause this error message. Common causes of this error are unexpected crashes or the power suddenly going out. Resolving crashing issues will help prevent the save data from becoming corrupted. Recreating the save file will remove the damaged files and create new ones with your account data.
The easiest solution is to select the New Save button. A new save file will not affect your progress or Inventory. Training Sequences, Video Settings, and Tutorial completion data will be removed with the following steps.
First, let's sync our device clocks to rule out any Sync Failure error messages: How do I sync my clock to fix Save or Load Failures in Rocket League?