Open Windows Features.
Make sure both ".NET Framework 3.5" and ".NET Framework 4.8 Advanced Services" are fully checked.
Open PowerShell as Admin and copy-paste the following command:
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V -All
If the above fails, then uninstall (followed by a Reboot) and reinstall (followed by a Reboot) Hyper-V completely via Windows Features.