Why is my phone not charging when the power light is on

@augustineiruedo if it never charges, always refuses to charge, it is time to check /change your battery. If you give us your proper model number, we can most likely give you a more specific answer.

Do not forget to check your power supply. Make sure it has the proper voltages. Check to make sure connectors are not bend etc. After that, check the charging port. Clean it of any debris etc, use a few puffs of air to clean it out. Make sure there is no corrosion, debris etc. that prevents it from working. If you checked that and none of this works, get a ammeter and see if your phone draws any amperage from the charger. After that, you need to check and see if your motherboard even gets power. For that of course, you need to disassemble your phone. Post Some good pictures of what you see. That way we can see what you see

Adding images to an existing question