Ciao 

have you tried to access the helper VM?

in the past, I needed to access the VM Helper to check for a communication problem (in my case the VM did not have the gateway configured correctly).
To access the VM Helper I used this KB (it is for a previous version of Converter):

Enabling Logging in to Helper Virtual Machine During Conversion of Powered-On Linux Sources with Con...

if it works you can access the VM-Helper in the console and check if it has network problems.