Chosen Solution
UE Boom must be left on charger in order to work. Once the charger is disconnected, the battery dies.
If your UE Boom 2 won’t charge or loses battery life quickly, see the UE Boom 2 Won’t Charge or Loses Battery Quickly problem page for possible causes and solutions. You likely need a new battery. Try a different charger as the one you are using may not be powerful enough to charge the battery. That is, if you are using something other than the charger you got with the speaker (5.1V 2.0A).
Try to Replace the Battery.. maybe the battery has a problem..