Just wanted to share this in case someone else is having the same issue, and going insane.
VMWare Converter Standalone 6.1.1 refused to convert a SLES 12.1 machine - constant error message of "Unable to query live source machine".
After looking into the log files and manually executing the data generation script, it appeared that the presence of grub2 was causing the issue, as the "--batch" property was no longer valid.
Instead of downgrading grub, I decided to try converter 6.0.0, which seems to work without issue. Once the migration completes, I will follow up if there are any other issues...