Why does turn off 10s after I turn it on?

When I plug it into a charger, the red LED stays on permanently, but the speaker still turns off if I try to use it. It doesn't seem to hold a charge, and even when plugged in, it doesn't stay on properly.

I've already tried:

Resetting the speaker (Volume + & Bluetooth button for 15 sec)
Using different chargers and USB cables
Letting it charge for hours before turning it on

None of these solutions worked. Does anyone know how to fix this issue? Could it be a battery problem or a firmware issue? Any help would be appreciated!