Followed up my original Facebook message with another one a week later - and this time a response!
They are sending me a replacement box which will hopefully resolve the problem.
One further question if I may - I've got a few recordings on the broken box that I'd still like to watch. Is there any way of transferring the recordings from the old box to the new?
An update, but another problem.
I plugged in the new box and switched it on. After some firmware updates it asked me for an Activation Code - apparently I should have been sent one by SMS, e-mail or post. As I didn't have one, I messaged Optus to ask for it, and thought I'd put the old box back in until I received it,
However, the old box now comes up with a message saying that it is not activated. I get the option to 'check network' or restart. Checking the network confirms the network / internet connection is OK, and takes me back to the first message. Restarting also just returns me to this message.
I then had a thought re the Activation code - I wonder whether the original activation code would work, and do I still have it? Well yes, there it is in my Text messages from 2015 (good job I don't change my phone very often) - and it works! So my new box is now set up and working.
However, I'd still like to watch some of the recordings off the old box, but plugging it in still gives the 'not activated' message, with no option to put in the Activation Code
Is there any way to get the old box to work again? Maybe some sort of reset so I can re-activate it? But without losing what's saved on there. Any ideas appreciated.