We’ve seen occurrences like yours a few times. Do you have access to any other computers you can attach it to for a few minutes to do the config? The software can’t be forced so if it is closing even with java installed then it could be an incompatibility with your 10.11 system. You can also do the conversion on a Windows system if you have access to that. Once converted you can bring it back to the Mac and format it.
Make sure you have the drive attached via USB when making the configuration change but it looks like it won’t work for you on El Capitan. If you have tried it on multiple systems and it behaves the same way.
Eventually did it on a Windows Box … but why I had too, shezzzz !!
Now some week or so later it is beeping 3 times constantly, orange lights on top drive and going offline/unmounting the partition.
If we reboot it … it seems OK for about an hour, then beep, beep, beep …
DUFF Device again from GTECH … this is the second in as many months