Local User in Local Group Admin

Hi Admin

I created a GP where I control the Local Administrators Group, this works fine and all my Security Groups in AD are Added to allow access to specific groups rather than people.

Now, I created a NEW Local User Account through the GP and that has been pushed out to the Desktop (VM) fine.

Now I am trying to Add this Local User to the above Local Admin Group (the BUILTIN\Admin group).

I tried this:

Is this incorrect? The Local User Account (Core.Local) does not seem to be added.

Thanks in advance

NN