From the screenshot it looks like at least the data collection part works properly. Can you login to the controller VM's console in NGC/vSphere client during Iometer runs and see whether an Iometer window pops up? If there is no Iometer window showing progress, it most likely due to unable to ssh/scp. Please try to ssh/scp from the controller VM to all the worker VMs (including the controller VM itself) and see whether the default root password works.
Thanks,
Chien-Chia