In recent Chrome versions (63 and above) the incoming call sound is not played unless you have the tab open and focused (doesn't work if it's open but not being viewed) which can lead you to believe you are not receiving the call notifications.
This new behavior affects all websites accessed using Chrome, not only Toky.
To prevent this from happening, we suggest a few potential solutions:
keep a Chrome window always open and with a single tab pointing to app.toky.co, or
download our desktop app
Also, make sure you have enabled Desktop Notifications.