The "Files Required to Play GTA Online could not be downloaded" error can occur when attempting to play Grand Theft Auto V (GTA V) online. Here are some steps you can try to fix the issue:
Check your internet connection: Make sure your internet connection is stable and that you have a good signal. If you're on a wireless connection, try connecting to a wired connection or moving closer to your router.
Restart the game: Close the game and restart it. This can sometimes resolve the issue.
Clear the game's cache: Go to the game's settings menu and clear the cache. This can help to resolve any corrupted data that may be causing the error.
Verify the game files: On Steam, right-click on the game in your library and select "Properties," then go to the "Local Files" tab and click "Verify Integrity of Game Files." This will check for any missing or corrupted files and repair them if necessary.
Update your graphics driver: Make sure you have the latest graphics driver installed for your GPU.
Disable your VPN or Proxy: Sometimes, VPN or proxy can cause this issue, try disabling it and then launching the game.
Wait and try again later: The error message could be temporary due to server overload, wait for some time