Laptop battery won't charge
This is very common, and most of the time it's the cable, the outlet or a setting rather than a broken battery.
Be careful: If the charger or laptop gets very hot, smells of burning, or the battery looks swollen, unplug it right away, don't charge it, and get in-person help.
What to do
Step 1: Plug the charger straight into a wall outlet you know works.
Step 2: Check the cable is firmly in at both ends. With MagSafe, check the light on the plug: amber means charging, green means full.
Step 3: Look gently into the port with a flashlight for lint, but don't poke anything metal in.
Step 4: If it says Not Charging or the battery stays at 80%, this may be on purpose. Your Mac pauses charging to protect the battery when Optimized Battery Charging is on.
Step 5: To charge fully now, click the battery icon at the top of the screen and choose Charge to Full Now if you see it.
Step 6: Shut the Mac down, wait 30 seconds, then turn it on with the charger plugged in.
Step 7: Check System Settings, then Battery, for any message about the battery needing service.
Still stuck? If it still won't charge, try a known-good charger of the same type, then contact the maker's support or a trusted repair shop, as the battery or charger may need replacing.