Cooler Master is the brand, while 750W is the wattage. What is the model of the PSU? Breadboard the system and work with the iGPU(motherboard's display ports) and see if you get display. If you do, disconnect the system from the wall, drop in the RTX 3060Ti and then try powering up the system.
Which slots are the sticks of ram populating on the motherboard?