The New-VM cmdlet requires an additional parameter: a resourcepool, a vmhost or a vApp.
Are these new VM to be created in a cluster ? If yes, then you better use the resourcepool parameter
Like this for example:
New-VM-Name"$name_$suffix" Template$template-OSCustomizationSpec$oscust-ResourcePoolResources-Datastore$dsc-WhatIf-RunAsync
This will create the new VMs in the root of the cluster.