If you can't make or receive calls, please change your settings as follows.

<For Both OSs>

• Restart the app or the device.

Note: After you restart the device, unlock the device to try making or receiving a call.

• If you usually stop calling in several seconds, please try calling for one minute to be connected.

Note: If the device of the other person is in sleep mode, it may take time, sometimes more than 50 seconds, before you can start talking.
Note: The time it will take before you can talk depends on the device capacity and network condition.

• Go to "Settings" on the device > Turn on "Airplane Mode" and then turn it off.
• Go to "Settings" on the device > Switch on/off "Mobile Data Communication."
• Go to "Settings" on the device > Switch on/off "Wi-Fi."
• Go to "Settings" on the device > Turn off "Do Not Disturb."

Note: If the "Do Not Disturb" is ON, an incoming call will be silenced and a missed call notification appears. (This applies if you use iOS 13 or later and the Integrated Calling is enabled.)
Note: If "Settings" on the device > "Do Not Disturb" > "Repeated Calls" is ON, a second call from the same person within three minutes will not be silenced.

• Go to "Settings" on the device > Turn on "Local Network."
  or Go to "Settings" on the device > "Privacy" > "Local Network" > Turn on "SkyPhone."

• Go to "Settings" on the device > "Network & internet" > "Advanced" > Turn on "Airplane Mode" and then turn it off.
• Go to "Settings" on the device > "Network & internet" > "Mobile network" > Switch on/off "Mobile data."
• Go to "Settings" on the device > "Network & internet" > Switch on/off "Wi-Fi."

Note: After you try them, change the settings back as necessary.
Note: The process can be different depending on your device model.