Need Help, getting a constant prohibitory symbol

I recently picked up a Mac Pro 4,1 (2009 model) from marketplace with no hard drive in it. I picked up an SSD, got it home, and downloaded OpenCore Legacy Patcher to install macOS Big Sur.

I followed this video:

https://www.youtube.com/watch?v=flQRKWBKC60&t=1046s

And I get to the point where I have created a flash drive with OpenCore installed to it, I plug that into my Mac Pro, boot to it while holding down option, and I choose EFI. From here, it launches me to recovery mode where I install macOS Big Sur and it brings me to a black screen to select either the macOS installer or the recovery mode. I choose the installer, and it puts up an Apple Logo with progress bar. This takes roughly 10 minutes or so, then shows the prohibitory symbol.

So, based on the trouble shooting section of the OpenCore site I try and boot again with Option held down, then choose EFI, and let the process run again. It seems like its installing macOS Big Sur again, and then it gets me to the same black screen with either the install macOS Big Sur or the hard drive option. I click the hard drive, the apple logo and progress bar appears, and ten minutes later I see the prohibitory symbol again.

So, using the above mentioned troubleshooting page again, I create the OpenCore bootable media on another drive. And I get the same results as before. What am I missing here?

Author: @andremamola810