New-NetNat : The parameter is incorrect.

Hyper-V on Windows 10 now supports Network Address Translation (NAT). The steps to set it up are documented in this MSDN article Setup NAT Network

But while running the New-NetNat command like the one below,

New-NetNat -Name MyNATnetwork -InternalIPInterfaceAddressPrefix 192.168.0.0/24

You might receive the following error

New-NetNat : The parameter is incorrect.

The error is misleading as it points to the parameter being passed.

On my machine the error was because of an existing NetNat entry. The way you figure this out is by running the command Get-NetNat. This will list any existing NetNat entries. You can remove the old entry using the command Remove-NetNat