Hello,
Please note that we specifically use Google Authenticator for the "2 Factor Authentication" on SignalStart.
If you are facing an issue with the process please contact us by mail at support@signalstart.com so we can assist you ASAP.
I suggest you check out the Signal Start website, which is also available in Japanese!
In addition, if you have any specific questions, feel free to contact us at support@signalstart.com.