Why does my iPhone only turn on when plugged into dock?

My partner dropped her into water a couple of days a go and was only in there for a few seconds.

The iPhone was not fully submerged in the water only the bottom half of the phone.

After which I turned the phone off and waited for the phone to dry. I tried to turned the phone on and was met with a blank screen, when I plugged it into a docking station it came on but when i unplugged it it immediately turned off.

I have tried the rice trick (naively), after that didn't work I bought a new battery and replaced the old one. That didn't work either. I then clean the whole logic board with some isopropyl alcohol and reassembled the phone.

I have ran out of fixes and hoping someone can help me.