Check the following points:
Handset battery is charged
Router is switched on.
Connected to the Internet (LED on Internet-Box is white)
No power failure
To ensure that you can still receive calls if there is a power cut or a connection problem, activate the supplementary service “Forwarding in the event of interruption” on My Swisscom(opens in new tab). You can set a number there to forward calls in the case of such a situation cropping up.
If the connection problem persists, please contact us.