black screen with dual monitor setup but works fine with single monitor.

I have setup my Hackintosh sierra and everything works fine.

except when i boot with 2 monitors it will start up and give me a black screen.

I can however boot with one screen and then plug in my other one to make them both work.

How do i make them both work on boot?

My specs are:

nvidia gtx 1060 6gb

i5 4570

16gb ddr3

asrock h81m-dgs