PC doesn't turn on when Commander Core XT

[CCartola]

Motherboard: ASUS TUF gaming X670E-Plus
Case: Corsair iCUE 7000X RGB (3 front fans + 1 back fan)
Pump: Corsair iCUE H170 Elite Capelix (liquid + 3 fans)
RAM: 32Gb Corsair Vengeance
Power Supply: Rog Strix 1000w

CPU: Amd Ryzen 9 7900X

When Commander Core XT is plugged to the Power Supply, PC doesn't turn on. Whenever I unplug them, it turns on.

I have replaced the motherboard (another copy), the power supply (2 more), the pump (with its fans) and the case (same model, with its own Commander Core XT and fans), none of them have worked out nor done any perceivable changes.

I have, just in case, replaced SATA cables (which are connected to both Commander Core XT, from pump and case, and an external SSD), to no avail.

I have tried to turn it on with and without graphic card (Geforce RTX 3090), as well as changing both RAM sticks' placing (and each one separately).

PC was working perfectly until last month. One day it was particularly hard to turn on (as pressing the power button wouldn't work for a few tries), the next day it wouldn't turn on at all, and so on.

Whenever it's turned on (without any ventilation), a menu appears asking for it, as the CPU may overheat, I haven't digged too much into it.

Please, any help?

Could it be a short circuit of some short from the power supply or the motherboard or is it just the Commander Core XT (both) that don't work?