Hi, guys! I had a similar issue: my oneplus was on around 15% when it just switched off. I put it on charge overnight but in the morning it did not turn on at all no matter how long i was pressing the power button.[br]
I went on some forums and saw ppl recommending to leave the phone on charge for 12h and try again - did not work. power button + volume down also did not work, nor did taking out my sim card.
When i pressed volume up + power though i saw a quick message on the screen that the battery was too low on charge (below 1 per cent). I then tried another piece of advice and put my phone on a charge via laptop - and it worked!
I charged it enough to turn it on and then transferred it to charge from a power socket - works now[br]
Uiii, i dont have to go to the repair shop[br]
Hope it will help someone ^^