The picture below shows the basic components needs to check if the phone somehow doesn't charge if the wall charger is plug-in. But you may first ensure that the wall charger and the phone's battery you are using are still working. A drained battery will not charge, try to plug the battery charger around an hour or try to replace it with a good one, to quickly check if the battery got the problem.
If the battery and wall charger seems no problem, have a visual check on battery connector and charging pin connector (DC jack) for possible damaged. Then proceed to PCB board or hardware troubleshooting to continue.
1) Clean the charging pin connector and terminal contact pads. Ensure that it is not misaligned.
2) Check the fuse for possible open circuit, replace if found damaged.
3) Check the diode for possible short circuit, replace if found damaged.
3. Check the charging transistors for possible oxidation build ups, clean, rework or replace if necessary.