You have not connected the power cable to your video card
Namely, we will touch upon such an error before loading the OS as “You have not connected the power cable to your video card”. How this is translated and what needs to be done - read below. Let's start, perhaps, directly with the translation of this ominous error. “You have not connected the power cable to your video card” - this is, in fact, what the text of the problem says.
Naturally, the solution suggests itself. Recently, powerful video cards cannot receive enough power directly from motherboard, so they are powered through a cable coming from the power supply. Sometimes the connector is four-pin, there are also six- and eight-pin connectors. The main thing is to supply power from the power supply through the appropriate cables to the appropriate connectors.
It is not necessary to use all six or eight “pins” - four may be enough. Using additional pins will increase power consumption.
Naturally, all manipulations with connecting cables must be carried out with the computer turned off and power supply. Otherwise, you risk getting an electric shock or losing your video card, power supply or motherboard, and possibly everything at once. Be careful! After carefully reading this article and following all instructions, the problem should be resolved. Good luck!