I have a Mac Pro 5.1 2010 currently running macOS El Capitan 10.11.6 and I wanted to update the GPU and after I checked Apple’s recommendations for GPU upgrades I just bought a Sapphire Radeon RX 580. So I removed the two old GPUs (ATI and Nvidia) and plugged in the two 6pin into an 8pin adaptor as shown below and put the new Sapphire as shown in the below photos. But seems that it’s not working as I tried multiple screens but they are not detecting any signal. Is it a macOS EL Capitan problem and do I need to update to Sierra or High Sierra first Before being able to use it?