Why is my phone not switching on?

Abigail,

If your led indicator comes on when the charger is attached, it is unlikely the charger port on the phone or the wall power supply are non-functional. However, it would be worth testing a new charger, one that is at least the 1.3Amperes your OEM Nokia charger is rated.

The next step in the diagnosis would be to open the phone. It has been several years since I have opened a Nokia N9. If I remember correctly though, you can remove one screw from inside the SIM tray area, then the screen will be free to unclip from the plastic outer frame and interior metal body of the phone. This generation of Nokia uses torx screws - t4, t4, t6, etc. A 0.5mm or 0.6mm guitar pick is excellent at unclipping the screens from these unibody Nokia's.

The first thing to test would be the phone's battery. If your battery is below 3.7Volts, than you cannot expect the phone to start. Above 3.7V, with good hardware and no software issues, the phone will start. If you are able to read the battery voltage, try plugging in the charger for at least ten minutes before reading the battery voltage again. If you start at one voltage, say 3.5V and the battery charges up to 3.8V, than the battery does charge. Investigate the possibilities of a software problem or faulty display hardware. An installed screen is not required to charge your battery. Make sure the battery is not plugged in before reinstalling other parts such as the screen. Your battery should be the last thing plugged into any system.

If you read 0V the first time you test the battery, you should still try plugging the phone into a charger for awhile and then checking the voltage a second time. If the voltage is still 0, your system is not charging. If you have access to a new battery, plug it in and repair the above steps. If the new battery still does not charge, your next step would be to replace the charger port and repeat your tests.