Mouse and keyboard sometimes don't work after booting

I built my new gaming rig about a week ago. Everything worked great for the first few days, but then I started getting this problem that when I booted my PC, the keyboard and mouse sometimes don't work at all. They have about 50/50 chance of working. It's the Corsair Strafe keyboard and the Corsair Sabre RGB mouse, both plugged into the Asus STRIX Z270F ATX LGA1151 motherboard. The PC is running Windows 10 Home 64-bit.

The keyboard and mouse are definitely getting power because the lights on them light up, but the keyboard's light setting switches to the standby one, as if the PC is off. It happens during booting because I can always get to the UEFI menu and use it. I've figured out that unplugging both peripherals and plugging them back in makes them work again; however, that's obviously not a long-term solution to the problem.

Does anyone have any idea what I could try to fix it? I'm currently on holiday (poor timing, I know), so I will be able to try out any and all suggestions when I return. I just thought I'd write this now while all the details are still fresh in my mind.

Thanks in advance!

swarfega said:

Hi and welcome.

Did you install the Corsair CUE software?

I've also found that the keyboard (K70 in my case) prefers to be plugged into a usb 3 connection at the back of the computer.

Thanks for replying,

I have installed the software, and both the keyboard and mouse are plugged into USB 3.0 ports at the back.

swarfega said:

You could try various usb ports and see what results you get. If it still fails, consider getting an external powered usb hub. After that it may be the keyboard at fault. Do you have another usb keyboard to test?

I have not tried other ports, but I don't think it's the ports' fault since the mouse and keyboard definitely have power, they just don't get that the PC is on. An externally powered USB hub also won't help much for the same reason, the peripherals are certainly drawing power.

Testing with another keyboard is a good idea, I'll do that when I return home and get back to you. :)

swarfega said:

It could be fast boot. You could try going into bios and turning that off.

Another good idea! Thanks. :)

Turning off fast boot appears to have solved the issue. Two days without a hitch. Thank you!