Thanks for reporting this to us, @zzcool500 - I really appreciate you coming back to us.
The testing we've done on our end had confirmed that Valhalla was working just fine with Windows 11, so it's really unusual you've ran into this issue. In this case, I'd like to request that you reach out to our support teams with some system files, as these will allow us to capture some information about why the game isn't launching, and investigate further.
Please see this support article, which describes how to generate a couple of system files. You'll then be able to contact us at the links below to get those files across to us. Please include your Ubisoft Connect username or email address in your message to us, as well as a link to this forum thread, so the support agent on the other end can help more quickly.
https://ubi.li/support
https://ubi.li/twitter
https://ubi.li/facebook
Please let me know if you have any trouble generating these files, or getting in touch, and thanks once again for reaching out. Let me know if I can clarify any of this post at all!