I found a solution on Reddit which worked for me.
Log into the game, disconnect from the internet, reconnect, go back to Unbound and make sure it's in offline mode, and then click to go back online. It should reinstall all the inventory correctly this time. At least, that's how I fixed it. Got the issue a few days ago and that's how it stopped.
Product: Need for Speed: Unbound
Platform: Xbox Series X
Gamertag: DILLBRICK
Summarize your bug Error code F03, Won't load multiplayer.
Seems to be reaching rank 27 and unlocking a specialised Honda Civic in update 9, Have Ultimate collection, Other plausible theories are bugged out after getting a Bugatti Chiron in Lockdown or buying R35 GTRs to use for the game mode.
How often does the bug occur? Every time (100%)
Steps: How can we find the bug ourselves? Getting kicked out online, relaunched the game, try to join a multiplayer game from online garage.
What happens when the bug occurs? Can't Modify or Buy/Sell anything and not able to play online multiplayer.
What do you expect to see? Instructions to be able to play online multiplayer again to play multiplayer and collect the blacklist cars from update 9
Troubleshooting steps taken before posting: I have currently uninstalled the game and all the DLC (including the Ultimate Edition Upgrade) Hard Restarted the Xbox (Turned off the console and reboot), Re installed individual dlc, Haven't resorted to selling cars yet as I can't do that.
To everyone experiencing Error Code F03, Check if this works, It did for me.
