Sorry, I can't quite make sense of the last pgh.  I think you meant to say that when you plug in the 9020, it used to power up the fans and power light for a couple of seconds and then shut off?  That's a self test it does In the first post, you said it's been working fine for a week.  Does this mean it turns on now with the front power button? Before it was mentioned that it's been running fine for a week, and as long as the power button is fine, it sounds like a PSU on it's way out. First thing I would try though is replace the size 2032 CMOS battery if it's 5+ years old.  Bad batteries cause bizarre problems even if they seem unrelated.
Hello, I have an Optiplex 9020 computer. I shut down normally at night and when I started in the morning I did not start with the front button. After trying hard, when I started with a small button in the power supply, the computer started and everything is fine, the display is also coming and it has been working fine for a week, please tell me any solution. ۔ Thanks
Optiplex 9020 computer I started with a small button in the power supply