Are you talking about vRO or vROps?
For vRO you might want to post your question here;
For vROps you are in the right place. Which version are you running? Can you ssh into vROps?
set the VM to boot to bios then open up the console and close the bios and look at the boot up sequence. Hopefully you can see an error. It is not a true black screen as there is a cursor in the top left.