Hi, I have just join Optus NBN50 with 4G backup. Everything is setup correctly and the internet and the home phone are both working well. However, never had to use 4G backup yet. Not sure if it is working? The lights for the 4G mobile are all not lit up at all though there is a sim card installed. How do I know that the 4G backup is working? Should some of the 4G mobile indicators be lit up at all on standby? Perhaps those who have had a Ultra Modem for a while can shed some light on this? Thanks.