The WiFi adapter for the Miele appliances only supports pure WPA2 encryption.
WPA3 encryption and mixed operation using WPA2+WPA3 encryption are not supported.
Change your router settings to WPA2 encryption. Consult your WiFi router’s operating instructions for further information.
The system requirements for WiFi are available in the article at Miele@home > Miele app > System requirements for WiFi.