UUID error trying to convert VM

I am trying to convert a VM by vCenter Converter Standalone v5.5 (5.5.0 build-1362012). When I select the VM and press Next, the following error message appears: "A general system error occurred: Invalid Argument".

The log file shows the following error: "ManagedVmLocation does not have VM MoRef or VM UUID".

How can I solve this ?

Thanks.