If it doesn’t help, please use 12.1.4 lower version or another phone to setup teffo, after installation, use the same account and passwords on your 12.1.4 iPhone.
Due to some Android phones (above 8.1) have special configuration of WiFi settings, if you have problem when install teffo, please follow the steps:
1. Check the Android kernel version whether is v8.1 or above version.
2. If so, and fail to connect with teffo, please use iPhone or other Android phone which kernel is between v6.0 ~ v8.0
3. After installation, use the same account and passwords on your 8.1 android phone.