Hi, after many retries adding this repeater in Mi Home, I found that the problem was that my Thomson TG784v3 had security mode set to "WPA-PSK + WPA2-PSK" instead of "WPA2-PSK". After this change, Mi Wi-Fi Range Extender Pro configured properly and added successfully without any retries or issues to my Mi Home account.

Xiaomi should add this information together with the 2.4GHz Wi-Fi limitation in troubleshooting hints.