you pulling to much power and re plug in yore start button read properly the format to plug in only try wit start button plug in or invest in a bigger power supply and unplug some fans
had an issue almost the same as that, pc only starts when the power button is held down when the button is released it turns off... found out i forgot to plug in the four pin power on the mobo...
It sounds very stupid but make sure your aio water cooler is pushed in properly because my brother had that problem and I had a look and it was his cpu block take it off and try push it on and do it properly
It should be the ram stick or the aio or the processor itself. Since it start and off. For the case not turning on possibly the power pin havent connected to the mobo. Sorry cant help much but tats the only thing i can deduce from the video above.
Could be bad PSU
Had literally same thing on my comp after swapping gpu and RAM
Everyone said check ram but turned out my psu got toasted after switching power button on and off