Wont go on unless on computer

so my player went off. if i plug it in it works, eject it just fine. but if i unplug it then it goes back to black screen. help. tried resetting it. didnt work.

The battery is dead or not connecting properly—replace the battery or check its internal connection.

Replace the battery or use an external power adapter to keep the device powered; this is usually caused by a worn-out battery.

Try replacing the device’s power adapter or battery; in many cases, the issue is actually caused by a malfunction in the internal power supply module.