Bios won’t display on external screen using Alienware 17 r3

I have a Alienware 17 r3 that has display problems. I recently replaced the motherboard and the display does not come on. Windows recognizes it but when booted it doesn’t do anything no logo no bios no windows. I have connected and external display and that does work however. I cannot go-to the bios and check anything because it will not show me the bios. It comes on just as windows loads the login screen. I’ve tried everything I can think of but it won’t display bios. Any ideas?