Why does the battery icon on my phone keep flashing and why won’t it charge?

Your battery is low. Recharge or replace the battery to continue using the device.
The battery terminals may be dirty. Wipe both gold colored contacts with a clean, soft cloth and try charging the battery again.
If the battery will no longer charge completely, dispose of the old battery properly and replace it with a new battery (refer to your local ordinances for proper disposal instructions).