Black screen on FileVault reboot Mac Pro 4,1

[SolidCake]

Hey guys,
Ever since I got my Mac Pro 4,1 and flashed it to 5,1 I am unable to encrypt the main drive using FileVault. When I enable FileVault and reboot from the reboot prompt the Mac boots to a black screen and stays black. My Mac Pro is currently on macOS Sierra but I have had the same issue with El Capitan.

Mac Pro 4,1 -> 5,1
2 x Xeon X5690
32GB 1333MHz DDR3
Sapphire HD 7950
macOS Sierra on Samsung EVO 850 500GB

Can you guys please help me out?

 

[-VoiceOfReason-]

FileVault presents a login prompt at the boot screen to decrypt the drive and start booting. If your card/monitor configuration doesn't support displaying the boot screen, you'll have to figure out why.

In the meantime you could try putting in your password blindly and see if it boots.

 

[SolidCake]

That sounds like what is going on! I have had the same problem with the stock NVIDIA GeForce GT 120. So, this could be a display issue as I bought a UltraSharp UP2516D with the Mac Pro. I'll try it!

What is the best way to go about logging in blind?

 

[orph]

sounds odd, if it's an apple GT120 then you will have boot screen, do you have a second display to try?
might be worth asking on the apple forums