Have you tried ‘Launch Workflow Interactive’ activity to invoke your workflows instead of ‘Invoke workflow file’. I believe this basically works even when the vm is minimized or closed.
We had a similar issue where when VM is minimized or closed, Elements were not being identified by the workflow and got it resolved by simulating all the activities and replacing Invoke Workflow file to Launch Workflow Interactive.
Hope it works for you as well.
Thanks,
Rammohan B.