Thank you for your invaluable support.
The handsets got correctly registered to the GO-Box 100.
Unfortunately, the handsets don't correctly take up the telephone line from our Swisscom Router through the GO-Box 100 base. Hence, I'm afraid the GO-Box 100 (connected to the Swisscom Router) doesn't carry the correct line configuration from the Router (telephone numbers, internal headsets etc.).
I think I should do the following:
1. Disconnect the base from the ethernet line, but not from the electric outlet
2. Reset the base
3. Reconnect the base to the ethernet line (and so to the Swisscom Router)
4. Register the handsets to the Base again
Would you please let me know your expert opinion about this matter?
Have a great day.