I am unable to get my 2009 Mac Pro (5,1) to recognize this card. A little history, I am running High Sierra. I am on the correct boot rom for the current version of High Sierra. I installed a new SSD hard drive, downloaded Sierra from the Apple Store used makeinstaller and created a usb bootable apple genuine boot drive. I installed Sierra on the SSD and then did an in place upgrade to High Sierra using the apple download, it asked me to perform the firmware update, I performed the update and checked to make sure I was on the correct boot rom after it booted into High Sierra. My machine is using an ATI 4770 currently and works fine with this card. The video card in question works fine on my backup Windows 10 PC that I have with a A10-6800k processor. The video card in question works fine in my I7-4770k hackintosh. The video card powers up and fans spin, the card has lights and those light up as well in the Mac Pro. I am unable to get video to work on the card using any of the following cable configurations... HDMI, DP, DVI. I have checked and verified that the cables work on my 2 spare PC's and the DVI cable that is being currently used on the Mac Pro with the ATI 4770 works fine as well on other PC's. I have tried SMC Reset, PRam Reset with no promising results. I have removed all PCI based cards in the Mac Pro and tried slot 1 and slot 2 and still a blank screen. I have tried 2 separate monitors that I know work on other PC's and the current Mac Pro with the ATI 4770 video card. Here are some pictures of the video card in question. Any reason it shouldn't be working? Any other steps I can take?