It is highly recommended that you add a Gmail account or email address as alternative ways of logging into your ClassDo account.
Check that your country code and mobile number are correct. If you have chosen the wrong country code/ entered a wrong phone number, click Back to re-select the country code and re-enter your mobile number.
The country code selected corresponds to the flag icon currently displayed. If it is not the correct country code, click the flag icon and select the correct country from the drop-down list.
Ensure Flight/Airplane mode is switched off on your mobile phone. Move to a location with better signal connectivity such as an open space and avoid underground locations or tunnels.
Check with your service provider if there are any issues with your current cellular network. You may also check if you are successfully able to send or receive messages from others.
Restart your mobile phone. This will refresh your mobile phone's cellular connection. Then try logging into ClassDo again.