Check list for conversion of Linux machine
1. Vmware Vcenter Converter Standalone Client version 6.0.0 build=2716716
2. Ports open 22 and 443
3. check if u are able SSH from destination. user should be part of admin group in Linux or Root should be enabled via remote (it is disabled by default due to security)
4. IP address of destination LAN is required on Helper VM
Let me know if you comply with above point and still not completing ....
Regards
Pankaj Sharma