So, I bought 2 1080ti's off eBay and they arrived today. Problem is that they aren't working, neither of them. When I try to boot, the vga led lights up red on my mobo for about 15 seconds, and then the boot device led turns on, and the bus led turns off, as Well as getting an A2 code on my Asus mobo. Whilst this is happening, I get a black display on my monitor, as is there's a signal, but it's only showing black. Please help guys, anything is appriciated!