If your iPhone, iPad, or ...

There are many different solutions to find for that problem but nothing worked for me.

E.g. If your iPhone, iPad, or iPod touch won’t connect

I still got an error message that my password was not correct. No matter what I did.

My solution was to open the website of my router ( e.g. http://192.168.0.1). There I looked up my phone in Network Devices and it showed my phone as in a active.
It also showed which Frequency it was using (5 or 2.4 GHz).

My solution is very simple. I changed the WiFi channel of my router from “Auto” to a dedicated channel (e.g. 4) – and I could log in immediately.

That’s it.