The tv stopped showing suddenly (repeatedly) and saying that "Television signal has been lost". It would restore services in a few minutes.
The cable is firmly plugged and it's not related to the internet connection. The problem started since last week.
Any idea what has gone wrong?
It means the box isn't getting an internet connection. If it's just one box, it's likely the connection between the box and the Telus installed router. Reboot your Telus router or gateway and then reboot all the boxes ONCE. If you get the same message on the screen, call Telus. If you restart the box too many times without an internet connection it triggers it to reinstall the operating system and without a connection, it'll fail and the box may need to be replaced.
Call Telus if the basic troubleshooting doesn't work.