Hi,
1. Have you proved that the wall outlet is working?
2. Have you tried a different compatible wall charger?
3. Have you tried connecting it to a working PC via a USB cable and see if starts to charge?
4. Have you tried a different known working USB cable to see if it works?
If you have tried'' all ''the above options and your phone still fails to indicate that it is charging then it is either a faulty charging port in the phone, faulty charging circuit in the phone or a faulty battery.
Hopefully this will help you to find your problem