Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
This could be a bad battery, or a bad ac adapter (not charging).
Unfortunately the internal battery is not replaceable or user serviceable.
If you have a meter handy, you can test the power adapter, or try recharging it instead from a computer via usb cable.
If still no change, then there is a deeper internal fault (bad battery, faulty power supply board, etc), which would ultimately require repair/replacement.
As this is a 2014 model, you're hopefully still under the 1 year factory warranty and can file a replacement claim with Sony. If beyond the 12 month warranty period, it would be less costly to buy a new system than to repair this one. There are no parts readily available and labor costs alone would be more than a new system.
If you'd like though I'm happy to help with replacement recommendations or finding a repair shop.
Best regards, ***** ***** for the news,