iPod Shuffle 4th generation - red light and not charging
Assuming the battery is still able to hold a usable charge, restart your iPod Shuffle. The red light typically means less than 25% charge.


  How to force restart your iPod shuffle
  
  
  Unplug your iPod shuffle from its charger and from your computer. 
  Use the power switch to turn off your iPod shuffle. If you see green by the switch, your device is on. (Can't find the power switch?)
  Wait for ten seconds. Then turn on your iPod shuffle again. 
  


If this does not work, it is likely the internal battery has failed.