Hi
Before giving up, try to measure the voltage on the battery terminals.
A working battery should have at least 3.8V. If the outpus is close to 0v, then the battery is dead. The phone will not start with a dead battery, even if the charger is plugged in.
Has the same problem with a Nokia phone. The phone got dunked. Lithium batteries have internal circuitry to protect against short-circuit. Once the fuse on the battery management module blows, it’s game over for the battery.
Good luck!
Bogdan