A. Ensure that you have a stable internet connection. Try switching between Wi-Fi and mobile data to see if that resolves the issue. If the problem persists, clear the app's cache by going to Settings > Apps > Sarku Japan > Storage > Clear Cache. Restart the app and attempt to register again.
B. Check if the app requires any specific permissions that may be blocking the registration process. Go to Settings > Apps > Sarku Japan > Permissions and ensure all necessary permissions are granted.