The solution was with https://communities.vmware.com/thread/428221?start=0&tstart=0
There are actually 2 solutions:
a) add into the "Add a NIC" Workflow into the script "add NIC" the line
nic.itemResource.resourceSubType.value="VMXNET3";
between the var nic = System.getModule.... and var nics = vm.getNetworkCards();
b) Change the createVirtualNetworkCard Action.
by adding a new String CardType and changing the line:
resourceSubType.value = CardType