Hello there,
As we have had no reports of this issue with the installation error during “Seas of Fate” persisting for some time now, we will now be locking this thread.
If you have encountered this error in-game, can you first check that the installation of Assassin's Creed: Valhalla has been completed. You can check this by going to Notifications > Downloads on your console. If the game hasn't finished installing, please let the game fully install before playing any further. You should receive a notification when the game is fully installed.
If the game has been fully installed and you are still encountering this error, it could mean that the game files have been compromised due to the game being launched before installation completed. To troubleshoot this issue, please fully uninstall the game from your console. We then suggest that you try the troubleshooting steps provided on the support article for your console:
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