I don’t know whether this is a Pi thing or a Volumio thing, but we had a power cut yesterday and no Volumio is not showing on the network. Can anyone advise?

SD card damaged?
Try disconnecting power (USB connector from Volumio), wait 10 seconds, reconnect and check.
If problem persists, reflash image.

I already turned it off at the mains for an hour before switching it back on again and it isn’t visible on the network. It happened once before and I had to reflash the card. Is this expected behaviour? Would it happen if I switched the Pi off at the mains before shutting down Volumio?