Having exact same issues with palit and kfa2 1660s, did you find a fix? Tried everything you have already. They work when directly in the mobo.
Thanks for the quick reply. When I put both my 1060 or 1080ti in the exact same risers, the fans work. However put either the 1660 super palit or kfa2 in the same risers, the fans don't work. The 1660s work perfectly And get a hash rate of about 32 but the fans don't work at all... Its very confusing.
Usualy a riser issue.
Check if their deliver pcie voltage.