Why am I missing inventory or progress across my accounts in Rocket League?

Each platform you link to your Epic Games Account shares its inventory with your other connected platforms. However, there are a few exceptions. Refer to this article: Which Rocket League items can be shared across linked accounts?

To ensure all the items from your different platforms are synchronized with your Epic Games account, follow these guidelines:

• Link all your desired platforms to your Epic Games account: https://www.epicgames.com/account/connections (Opens in a new tab)
• Launch the game on every platform and make sure you make it to the main menu screen to claim any items
  • This needs to be done on every platform that is linked to your Epic Games account

If you are missing items that are shared between different Epic Games titles, please refer to How do I get my Fortnite, Fall Guys, or Rocket League progress to sync across all of my devices?