Won't turn on before and after replace charging port

My friend’s JBL Pulse 2 had broken charging port. When you pressed the power button it still did flashed lights and gived the startup sound, but power LED wasn’t staying on. After dissasembly the speaker i found that chargin port was completely detached from the board. I replaced the charging port but there was no reaction on the speaker (should light up the leds on the right side. I opened the speaker more to get access to the mainboard and i measured the voltage of the battery, it was 3.2V only. I connected the battery to lab power supply and i charged it slowly by 100mA up to 4.2V as it should be. Still, the speaker only blinks with lights and gives the startup sound, not remains on. What may be the reason?