Do you leave the cable in the jack socket when you finish playing? That will run down the battery.
When you have changed to a fresh (fully charged) battery does the bass play/sound normal, at least initially?
It could be a bunch of things, but most are likely to be simple fixes. First suggestion is to use another cable if you have one. Then it’s time to take a look inside the control cavity of the bass in question. I am not familiar with the model you describe, but I’m sure somebody who is will be along soon to help you out.
Report back with any findings.