Given the same happens with SIV I suspect either there is a hardware issue or the firmware is in a funny state. What firmware version does your H100iGTX have (it's listed on both [Link Test] and [Link Status])?
First it would be sensible to see what happens with [Link Test] and see if you can use [Link Fans] to change the fan speed. Set Fixed PWM and PWM 25% then press [Apply].
What are the Current, Average, Minimum and Maximum fan speeds (post the [Link Fans] panel)?