R7000P power outage fault

I recently had a power outage for all of 20 seconds and, even though I’ve had many over the years with this router, this time the WiFi didn’t work again and the name of the router started showing up as the standard name instead of what I personalised it to. 
That is to say, my devices SAY they are connected but there is no actual, working WiFi. 

I’ve done all the usual work arounds suggested online and even resorted to factory resetting TWICE and I can never get to the end of the set up process in the app. I get as far as the ‘checking cables’ part which clears but it always says there’s no internet connection despite the fact my phone is showing as connected. It suggests turning the router off and on again - which of course I have done a hundred times.

I’ve checked my Internet service and that’s all perfect, as it’s displaying on the nbn modem.

Firmware was up to date even before all this nonsense and shows as such in the app.  

It makes no sense to me why all of a sudden it chooses to blow up after a power outage when it’s survived dozens in the past. 

I genuinely have no idea what more I could do. I know it’s an old machine, is it just time to upgrade?