LG Stylo 3 will not turn on T-Mobile

[mrr5745]

I was using my phone this morning and it suddenly turned off. It was at 87% battery. I've managed to get it to turn back on a couple of times since then, but it turns back off within seconds. Again - the battery is still showing charged - it was at 84% when it last turned on. When it does this, it's really dead - like the little red light for charging isn't even on. I've tried doing a factory reset to start it in boot mode, but that doesn't work either. Any ideas? Please help!

 

[mikedt]

Could be the battery has failed, although this phone is less than a year old. Should still be under warranty though.

 

[mrr5745]

They said the warranty is void because there's a scratch on the screen. I switched to Sprint and bought a new phone, but would like to salvage this one as a back up if possible.