Fixed my problem. one of the connections were loose.
Re: Computer turns on but does not boot after new PSU installation.
Nevermind guys, I just fixed it myself. What was wrong was that there was an 8 pin power connector not plugged into the motherboard, as my old power supply had a 4 pin power connector, and I had automatically assumed I didn't have to plug anything into it. There was a little platelet, covering the rest of the 4 pins so I didn't know I had something to plug in there.
Have this exact same problem but only have a 4 pin connecter and not another one.
So is it fixed, or not?
So your motherboard requires a 8 pin connector, but you only have a 4 pin connector?
I fixed it, forgot to update the thread though.