Will only work when plugged in, does not work on batteries

I have a JBL Flip 3. After a few months of use, now it only works/turns on when connected to a power outlet. When I remove the charger chord, the speaker turns off. Then if I try to turn it on when not connected to power, it turns on as long as I push the power button. As soon as I let go of the power button, it turns off.

Please kindly help me to solve this problem. Thank you!