We've fixed the problem in making a call which was caused by the server failure from 7:40 pm on May 30 (JST) .
Would you please try again if you found the problem?
Note: We are afraid that the problem might still occur on some of android devices.
Note: The service might be unavailable on some of android devices.
Please wait for a while till all of you can use the service as usual.
We apologize for the inconvenience and thank you for your patience.