Check the battery meter. Charge the phone if necessary.
If the phone turns on but powers down as soon as the charger is removed the battery is drained/bad and needs to be replaced. See Battery Replacement Guide.
See Battery Replacement Guide.
If a new battery has been installed and the phone still does not power on, the motherboard may be damaged. See Replace Circuit Board Guide.
Verify that the charger is firmly inserted.
It is possible the battery has been drained and needs to be replaced. See Battery Replacement Guide.
Verify that the LCD screen is correctly connected properly. See Replace LCD Guide.
If the LCD screen is properly connected but still not functioning, the screen may need to be replaced. See Replace LCD Guide.
See Replace LCD Screen Cover Guide.
Verify that the keypad cover is correctly installed and not damaged. See Replace Keypad Cover Guide.If necessary, replace the keypad cover. See Replace Keypad Cover Guide.
Verify that the keypad sensor is correctly installed and not damaged. See Replace Keypad Sensor Guide.If necessary, replace the keypad sensor. See Replace Keypad Sensor Guide.
Go to an area of better reception.
Verify that the antenna is not loose or broken. See Antenna Replacement Guide.
Verify that the microphone is properly connected. See Microphone Replacement Guide.Replace the microphone. See Microphone Replacement Guide.
If problems persist, the motherboard may damaged and needs to be replaced. See Replace Circuit Board Guide.
If necessary, replace the keypad cover. See Replace Keypad Cover Guide.
If necessary, replace the keypad sensor. See Replace Keypad Sensor Guide.
Replace the microphone. See Microphone Replacement Guide.