If your workflow show no logs, it's most likely something wrong with the conditions.
It should show in the log if it's executed. Try running with only LifeCycle state event to confirm this.
Second, I'm quite sure you must run the EBS workflow as blocking. Or else any parameters will not be updated back to vRA before the execution of the next event. (EG: Triggering Poweron will be run before your EBS workflow is finished.)
Futher more try to run with virtualMachineEvent instead of virtualMachineAddOrUpdateProperties. (virtualMachineAddOrUpdateProperties seems to change behaviour between different versions of vRA. I had it working in 7.0 and 7.1, 7.3 does not updates the properites between the different events. Running 7.6 now, not actually tested it here).
Add an output property to your workflow:
then set it to:
virtualMachineEvent = "BuildSuccess"
This is working in 7.3 atleast, however it will then skip any EBS workflows using VMPSMasterWorkflow32.MachineProvisioned or VMPSMasterWorkflow32.VMPSMasterWorkflow32.MachineActivated
If you want to see more details, you can have a look at my notes here: