Hello Marcelo,
The VM might be running. Please, power off the VM and try converting again.
Before converting a virtual machine or an image file, check whether the following prerequisites are met
Network adapters are enabled on system boot
Network adapters have IP addresses assigned over DHCP
RDP or SSH are enabled
Firewall is set to allow for remote connections over RDP or SSH
The VM that is to be converted is powered off
Retrieved from:
https://www.starwindsoftware.com/v2v-help/Cloud.html
Please, provide us with the logs if you are not able to convert a VM after powering it off.