1) Check the cable, use different cable
2) Check the charger, change to different charger
3) Check the power socket, try on a different charger
Feeling lazy? Skip 1-2-3 just go to 4.
4) Try to plug the same cable to a different phone. IS it charging?
If yes, then it's not problem 1-2-3. If no, then try check 1-2-3 step by step.
When you complete the isolation check and it's not the cable, charger and power socket issue, this leaves the USB port - battery to check.
5) Try shutting down the phone, remove the battery & replace it back. Turn on & charge again. I do this most of time to check whether it's firmware issue, charging icon not showing or battery 'jammed'. Sometimes works, just like our infamous bomoh, you never know haha
Step 5 not working? Then it's probably some problem with USB port. The most common issue is the dust particle blocking up the area surrounding the USB port from making a proper connection to charge.
credit to MYsimplefix dude, watch his video here.
Now, it's recommended to get a needle instead of toothpick for this job. Toothpick is too thick and we might spoil some parts of the pins inside the USB connector. First, power down & remove battery.
Using a needle gently scrape above highlighted area, stop if you feel anything blocking. Then use a clean brush to pick up loosen dust or fuzz, give it a gentle brush. Repeat few times, and blow out with air gun if you have, else give it a love blow haha. Careful to keep it dry from your saliva
All done now, pop back the battery and plug the USB charger cable.
If above doesn't fix the issue, then might be some issue with usb port corrosion, do so at own risk ya. Or the battery is simply konk out already..RIP battery. It's better to bring over to service center but ask how much is repair cost. If too expensive, just go for a new phone.