Having the same issue.
Repeater says connection opened but 5 commands waiting and it just sits there never changes.
Have tried multiple USB cables and used the driver mentioned above for mac got the serial port listed but can’t get the communications going.
Have the LCD installed and can move the machine around through the menu but can not get the MAC running El Capitan communicating with it.
By the way just got the machine about a month ago. Just got parts printed and put together. Electronics are bundle from vicious site.