Question CoolerMaster MasterboxQ300L Fan not working?

[FrazzledBoi]

So I recently built an office PC for my mother which is working perfectly until I noticed one issue, the fan that came with the case is not spinning. I noticed when I turned on the PC the fan would do a little spin and then stop, as if it were trying to move. The fan is 3 pin and I plugged it into a 4-pin header. Does anyone have any reason why this might be happening?
MotherBoard: ASRock B365M Pro4 LGA 1151 (300 Series)
Power Supply: Corsair CXM 550W 80+ Semi Modular Bronze Certified ATX Power Supply

 

[Darkbreeze]

Yes, it is probably not plugged into the 4 pin header correctly, not set to DC mode in the BIOS OR the four pin header does not support a three pin DC controlled fan.

Check to see that the "key" tab on the fan connector is lined directly up with the matching keyway on the four pin header. If it is not, then move it over by one pin so that it is. If it is, then you may need to go into the BIOS and check to see whether or not the options allow you to change from PWM to DC mode. PWM mode is likely the default, so you will need to change that fan header to DC mode if it is not already set to DC mode and if that board gives you the option to do so. Not all boards do, but most MODERN boards can be configured either way in the bios.