First things first: if your device has been dropped, shows signs of leaking, or looks swollen, stop using it right away. A damaged battery can be a safety hazard. Also, if you've had it for a while and it's been through a lot, it might just be at the end of its life. Disposable vapes are meant to be used until the e-liquid runs out or the battery dies, whichever comes first. If troubleshooting doesn't help, it's time to replace it.