Chromecast not working?

Since yesterday I have spent at least 5 hours reading in forums, I just can't find a solution to my problem.

I've been living in a student apartment since yesterday. We have "house WLAN" that means I just had to plug in my FritzBox yesterday and had WLAN directly. That worked perfectly.

Then I wanted to set up my Chromecast - which worked - the setup finally shows "Connected". Suddenly an error message comes up that my iPhone can't communicate with the Chromecast and I should look in the data protection settings to see whether "Local network" is activated - it is!

I just do not get any further. I'll attach a photo of my television for you. This is actually the normal "start screen" as I know it. But when I go to Netflix etc. Now, he doesn't find the Chromecast.

However, my Chromecast is not displayed in the Google Home app either.

All the problem solutions that I have carried out on the Internet have brought nothing. Could it be that it is because of the "house WLAN", I'm really at the end of my game 🙄

Reset the Chromecast by holding the button down for at least 25 seconds until the light on the Chromecast flashes. Then let go and wait until it restarts.

Then try the setup again.

I can tell you almost with certainty that it will be due to the settings of the "public" WLAN. Such networks are usually not designed for this. Can you test it with a second mobile phone as a Wi-Fi hotspot?