Getting "Attribute xsi:nil not allowed on element pool, which is not nillable."

I'm trying to create a simple workflow that will provision a vm. the error message that I'm getting is below:

Attribute xsi:nil not allowed on element pool, which is not nillable.

while parsing call information for method CreateVM_Task

at line 3, column 2

while parsing SOAP body

at line 2, column 1

while parsing SOAP envelope

at line 1, column 38

while parsing HTTP request for method createVm

on object of type vim.Folder

at line 1, column 0 (Workflow: Create simple virtual machine / Create ConfigSpec (item0)#38)

ReferenceError: "vmResourcePool" is not defined. (Workflow:Navicure Create simple virtual machine / Create ConfigSpec (item0)#38)

Here is what I've done, I've duplicated a canned workflow and have made adjustments to the workflow to automate a vm provision. the workflow that I've duplicated is "Create simple virtual machine", I have kept all parameters except for vmResourcePool. when I go to run the workflow the above error message is displayed. I don't have any resource pools in my cluster, do I have to have Resource Pools in order to provision from vco? I would hope not. I'm wondering if there is something I'm forgetting in my workflow. Any assistance would be greatly appreciated.

best regards,

J.