This is because the battery isn't being detected by the board.
The video tips at https://www.facebook.com/watch/508313572839417/1042870469519715 will assist greatly with troubleshooting this issue.
1. Unscrew the hilt grip and inspect the battery. Does it make good contact with the battery contacts in the electronics?
2 Remove the battery by tapping the hilt against your hand to "knock" the battery out (do not use implements to pry it out as you risk damaging the battery, electronics or yourself).
3. Gently bend the battery contacts outwards so they are less flat inside the chassis.
4. Reinstall the battery, paying attention to the polarity (+ and - are marked on both the battery and the chassis)
5. Attempt to charge again.
If these steps do not work, please contact us at email@example.com
Issue 1 - Saber has no sound
Answer = May be in mute mode. Turn off the saber, then hold the button for 0.5 seconds to change sound volume.
Issue 2 - Saber loses either red, blue or green color does not light up at all, or has no swing or clash sounds
Answer = Charge the battery for one hour, as this is likely a low battery issue. Removing and reinstalling the battery may fix it if the issue is not related to charge.
Issue 3 - When charging, saber cues 'charging' then immediately indicated 'ready' The battery is not making contact properly with the plates inside.
Answer = Open the saber and carefully adjust the connectors so that the positive and negative both touch easily bending helps as well. if DIY buyer adding a dab of solder to positive pad helps for perm solution.
To wake the lightsaber:
Awake mode operation:
When the blade is lit, the power button operates thusly:
Grey Paladin shows how to Swap the inner cores during an unboxing video
Useful guide by Grey Paladin
credit goes out to him for the approval to use his video please view and subscribe to his channel