Hello.
I had this problem. I mount and dismount the PC several times. All was according to manual and youtube videos. When I plugged the power adapter the fan moved a little, then stopped, light in the power indicator switched on, but pressing the switch on button didn't work. I read that these computers had issues with the RAM memories. I removed one of the two I have. I tried again, it worked. I switched the position of the two memories, it worked again.
Just in case this is helpful for someone, I wanted to post.