Guys, i  need your help.

I have 8x Sapphire RX480 8GB Micron GPU with custom BIOS. Dualmining with 198MH/s ETH, 3950H/s SIA. Settings: 1150;875 2000;910. Virtual Memory: 60GB.
Now I tried do start ETN with this settings. But only 3 Cards are working.

00:23:28:915   1d50   XMR - Total Speed: 2286 H/s, Total Shares: 32, Rejected: 0, Time: 00:00
00:23:28:917   1d50   XMR: GPU0 767 H/s, GPU1 773 H/s, GPU2 746 H/s, GPU3 0 H/s, GPU4 0 H/s, GPU5 0 H/s, GPU6 0 H/s

What I have to change, that this will work with 7 Cards?