It seems quite common for people to miss this step from the KB
“bcdedit /set hypervisorlaunchtype off” step followed by reboot
Another possibility is that if the laptop is a member of an AD domain, GPO could be enforcing things like Credential Guard/Memory Integrity. If it is, I can't help you with that and you need talk to your domain admin.
If you did do the bcedit step and it is not a member of an AD domain, you could try reinstalling the Windows 11 Professional OS on the host machine from scratch. Some weeks back, another person with a brand new Lenovo Thinkpad had to do a clean install to make it stop detecting presence of Hyper-V; as the laptop was not a domain member and he said he did all the steps in the KB and turned memory integrity off.
