On/Off switch will not turn power off

Will turn on and not off with the same button? Try the power operation with printer disconnected from the PC. If the problem persists when in this state, it is a problem on the IC controller and is not a repairable item due to cost. Printers are cheap these days and repairing them for anything other a gear jam is not cost effective.

Ok, a really brief description you got there, so the answer will be big. There is two main things you go to do. One on your PC and the other is on another person's PC. first, you got to test your printer on another PC to isolate the problem. If it worked then it's a problem in your Printer driver, uninstall reinstall or update. If it still has the same problem, then you have to do the same on your PC, uninstall your Printer Driver, reinstall then if still has the problem upgrade your software. Still not working? you have to open-up your Printer, unscrew the screws on the outside then check the board if there is a burned IC or resistor. Maybe something you can barely see. The last option is for a technician to check it. Good Luck.