This JUST started happening 2 or 3 days ago. I get the black screen when I'm connecting to one of my 3 computers. It doesn't matter if it's to my Macbook Pro, Mac Mini server or my work iMac. Black screen for all.
I did find tonight that if I screenshare through Mac OS, it works, so there's something about an active monitor. But again, I had zero problems with this until very recently.
Does anyone know what settings I can use to connect to my server if it's headless?
I found a workaround that works for me. If I go to the Actions menu and choose to "lock" then suddenly the screen appears (plus I'm logged out of course). But can then log back in and all works fine thereafter.