Check all your connections first. BTW just because someone told you something is "fine" double check on it. So, check your fuses. Check your logic board and your power switch with a multimeter to make sure that it is getting power. Look for nay components that may be a. loose or b. broke off. Check all the connectors for proper placement and connections. Trouble shooting this error is difficult since it can be practically anything that may have failed. Start with power and the switch. You can use your multimeter to determine how your switch opens and close the contacts, after that you can bridge the switch and see if it makes a difference. Hope this helps to get you started.