Physical Obstruction. The case sometimes presses down on the phone’s buttons, not allowing the phone to function normally.
- Remove your phone’s case and hold down the power button for 30 seconds.
There is a good chance your phone's battery is depleted and needs a charge.
- Leave your phone plugged in to charge for 30 minutes. If it’s completely dead, it will take more time to charge enough to power on.
- Try a different cable, power adapter, and outlet if there is no change while charging.
- Try a different battery. If your phone is not charging, try replacing the battery. Most phone batteries are replaceable, though some are not easily swapped out. iFixit has guides for replacing almost every phone battery.
Bad Charging Connection
As we stuff our phones into dirty pockets or bags, debris such as lint and dust can build up inside the charging port.
- Clean out the debris with a toothpick or something similar to ensure a good connection to your phone.
Avoid using metal tools to clean out your charging port. They can scratch and damage internal connectors.
If you're not having any luck with a traditional cable, try a wireless charger. Your phone’s charging port may be broken or dirty.
- Leave your phone on the wireless charger for 30 minutes or more to ensure it’s charging. Double-check the outlet the wireless charger is plugged into.
Your phone could be powered on but the screen isn’t working. Check for physical damage around the edges of your phone. The phone may still work but the screen may be disconnected or broken from fall damage or a recent repair.
- Once the charging port is cleaned out, plug your phone into a computer to see if it recognizes your phone.
- Either your computer or your phone will make a noise, letting you know that the device is connected. You can backup and recover files from there.
Faulty Third-Party App
A recently installed app may be causing issues with the phone booting.
- Boot into safe mode (Android) and uninstall the app or game causing the issue, or use DFU mode (iPhone) to test if the phone is still functional and needs to be reset.
- If the phone is not in a stable state with its firmware, booting into some kind of safe mode helps to troubleshoot, repair the issue, recover files or reset the phone.
For Android-based phones
- To enter Safe mode, hold the power button. After a few seconds hold the phone's volume down button. Continue to hold it down until you see Safe mode on the screen.
- Once you’re done, exit Safe Mode by holding down the power button for 30 seconds. Some phones require tapping Restart.
- Recently installed third-party apps may be the cause of the unresponsive black screen. Boot into Safe Mode to check if your phone is responsive and uninstall the app at fault while you’re there.
- Use this How to Put an iPhone in Recovery Mode guide.
A factory reset is the last resort regarding software bugs as this will completely wipe the phone's personal data and reinstall the original operating system.
- Since factory resets will completely wipe your phone’s data, make sure you have a backup of your phone before attempting this.
- Follow this page on factory resetting your Android phone.
- Follow this page on factory resetting your iPhone.