Put your phone in charging for a night then try turning it on by pressing Power + Volume Down button together.
What usually happen with Li-ion batteries that they are not supposed to undercharge. There are circuits for that to prevent your phone from undercharging, but somehow your phone got undercharged. If this happens to batteries, they stop charging, but don’t worry, giving them enough time to charge simply brings them back to life.
When pressing Power + Volume Down button you are going in recovery mode. You can simply navigate in recovery with power and volume buttons and restart your phone. Hope this helps
