If you are running System Center Virtual Machine Manager 2016 and have issues trying to create a VM using a VM Template after a Windows Update due to The class Scvmm_EthernetSwitchPortInternalSettingData does not exist in the root/virtualization/v2 namespace. There may be an easy solution for you. Below is an example of the error code

Error (20408)
VMM could not get the specified instance Scvmm_EthernetSwitchPortInternalSettingData.InstanceID="Microsoft:Definition\1f59a509-a6ba-4aba-8504-b29d542d44bb\Default" of class Scvmm_EthernetSwitchPortInternalSettingData on the server HYPER-V.HOST*. The operation failed with error HRESULT 0x80338000 The WS-Management service cannot process the request. The class Scvmm_EthernetSwitchPortInternalSettingData does not exist in the root/virtualization/v2 namespace.

Recommended Action
Ensure the provider is running, and then try the operation again.

The solution may be pretty simple.

Reinstalling the VMM agents on your Hyper-V hosts is pretty much the way to go. After installing the agent from SCVMM installation folder. All you have to do is to update the Agent from SCVMM Console. A restart is NOT needed hence there will be no downtime required
Remember to refresh the host and then try performing the action again. This time you would be able to successfully create a VM using a VM template.