Question about Xiaomi Mi Smart Speaker

Hello together I can't manage to connect the speakers to my WLAN. I have also reset the Fritzbox. Doesn't help, Google Home can't find the WLAN and if it is found it doesn't connect. But Chromecast works with the same Wi-Fi... The speakers on my parents' Wi-Fi work. What setting on the router could this be? Thanks for the answer. Greetings Rahel