I have a similar issue. I also have the Z370 Gaming M5 mobo (however it is the MSI version).
I have the Floe Riing 360 Premium. My issue is that no matter how many settings I play within the bios or in the MSI Command Center I cannot get the three radiator fans to spin. I have complete control with TT RGB Plus software over the LED lights. I have gone through three replacements from Amazon all with the same result.
I have tried plugging into both the CPU Fan and the CPU Pump Fan, changed from PWM to DC and back. I have stressed tested my rig till the CPU temp went over 180 degrees Farenheit. No matter what configuration I try the fans will not spin.
Any ideas would be appreciated.
Thanks