You can only get up to four AMD cards on Windows 7. You need to upgrade to Windows 10. There is supposedly a patch workaround to get more cards working with Windows 7, but I couldn't get it to work with the latest AMD drivers.
https://bitcointalk.org/index.php?topic=712228.0All of my 4+ card AMD rigs are working on Windows 7 with no problem for more than 3 years. Try running the mod with administrator priviledges, its pretty weird that it wont work for you.
I did and it won't even boot in to Windows. Are you using the latest driver?
I've used 17.4.x, 15.12 (Non RX cards), 16.7.3 and are all working fine for me. You dont need latest drivers as they may still be buggy.
I was able to get five card in Windows 7 since I also have a 1080 and the Nvidia driver installed. When I run the patcher it warns that there is more than one version installed and quits. If I force the patch it won't even boot in to Windows. I switched to Windows 10 and all six RX 480/580/570 and 1080 cards work.
Hmm, never had a rig mixed with AMD and Nvidia cards. So that may be the cause on Win7.