14 R4 black screen when on

My fans were making too much noise, so I replaced the fans and disassembled by alienware completely. Once, I put it all back together, it is switching on but there is no display. The skull power button flashes red three time and then runs the fan at max speed. Also, it does turn on the keyboard backlit and suddenly shuts off the system. I made sure to connect all the cables back to where they were. Anyone who has faced similar scenario? Looking for some helpful advise.