when you press the power button?
Disconnect everything from the G4, including power, keyboard and mouse
Plug the power cord, making sure it is fully seated, keyboard and mouse, back in
Any reaction at all?
I have an OLD iMac G4 that was working fine, but I went to turn it on one day and it wouldn't power up. I took off the round bottom and cleaned any dust off, have replaced the lithium battery, and put it back together again. Still no power. Any suggestions?