MP 1,1-5,1 Unable to get Boot screen, safe mode

[cakey]

Hello,
I was looking at OpenCore Legacy Patcher - updating Mojave to a newer OS (on a new SSD), went through the procedure and got to reboot - boot opencore but ran into an issue.

So I reboot (or turn power on from shutdown) and press option/alt then get the chime and nothing loads up. The computer runs, but the screen shows nothing.
Tried with a couple of Apple wired keyboards, an Apple Bluetooth one - same. Tried with another monitor, same. Tried without the usb drive (OCLP) - same.
If I press the power button to turn it off, it the computer turns off straight away - you don't have to hold it.
I cannot get into safe mode either - had the same response with the power button turning the computer off straight away.

I can boot normally into Mojave.
I also tried command R - which worked only when the main drive was installed. If I leave just a blank SSD in, the screen is blank after powering up.
I also did an SMC and NVRAM reset - same issues.
I took out all things plugged into the computer bar power and USB Apple keyboard - same issue.

I bought the computer with Catalina installed and I wiped it and installed Mojave from time machine, which was on my other Mac.

Mac Pro Mid 2010
2x2.4 GHz Quad-Core Intel Xeon
48GB 1066 MHz DDR3
AMD Radeon HD 7xxx 3GB

So what could the problem be?

Thanks.

 

[DeltaMac]

I think the problem is the graphics card, which is not one of the cards available as an option with your MacPro.
Previous owner had installed that as an upgrade, but one of the results is that the boot choice screen is not visible.
Without that boot screen, you can't select the EFI partition to load the initial OCLP setup.
One fix would be to replace that card with an original card (such as a Radeon HD 5770) or, there are methods to flash non-OEM cards to provide the boot screen.