FlashForge currently has 2 firmware options for the Dreamer. I would recommend loading the 2.3 firmware, as it is much more universally compatible.
There's instructions on how to do it here:
viewtopic.php?f=9&t=3578&p=20030#p18457
After you load the 2.3 firmware, then I think you should have no problem connecting with Simplify3D