Hello there !
I apologise for the delayed update. It looks like a fix for this error message has been deployed, so you should no longer encounter this error when launching Assassin's Creed Valhalla from GeForce Now!
Can you please try launching the game again to see if the issue has been resolved for you?
If you're still experiencing this error in-game, please don't hesitate to update us within this thread so we can investigate this further.
@ioanxd100 & @MisticNite420 - Have you both experienced this error message when launching Assassin's Creed Valhalla via GeForce Now recently? If so, please can you let us know the last time you experienced this error message so we can look into this further.
Thanks!