I have recently bought an ASUS GeForce GTX 1660 Super, Phoenix Series graphic card. I have installed the card on an ASUS Maximus VIII Formula motherboard with an Intel i7-6700K CPU. My rig is powered by a Corsair RM750i PSU. I also have 2 hard disks, 1 SSD and an Artic Freezer 34 eSports Duo CPU fan. I have plugged the graphic card with a power cord from the PSU. When I power the computer on the red led turns on and the graphic card fan spins regurarly. However, when I turn the computer on I get the warning "Please power down and connect the pcie power cables" on the screen. I have tried to use a different power cord, unplug a couple of hard disks to see if it was an issue with the PSU not supplying enough power, to no avail. If I plug the monitor to the GPU integrated on the motherboard all works fine. Same if I use an older NVidia card which doesn't require a power cord.

Any suggestion on how to resolve this?