If the battery hasn’t been used for long time, it’s possible that the battery had been over discharged. In this case, the phone would have no charging indicator when you plug it to the charger, which doesn't mean the battery is broken. You can charge it for at least 10-30 minutes and see if there is anything changing.
If the previously described options do not help, you can contact our hotline or repair center to get more professional technical assistance.