iPhone 5S WiFi not accepting password (water damage)

Hi there,

I have an iPhone 5S which was water damaged,
cleaned in ultrasonic bath,

iPhone needed a restore after this.

iPhone restored, all is working, except for wifi.

The actual problem:

it finds the wifi-spots, but when putting in the password,
it does not accept it, says it is the wrong one (while it is the right one)

Anybody here have an idea how to fix this?