If the following message "Video calling is not supported in your current communication environment." appears, please change your settings as follows.

iOS

• Go to "Settings" on the device > Switch on/off "Mobile Data Communication."
• Go to "Settings" on the device > Switch on/off "Wi-Fi."

Android

• Go to "Settings" on the device > "More" > Switch on/off "Mobile Networks."
• Go to "Settings" on the device > 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.