Does the display still shows cover art or has it stopped working completely? There is also an option to switch off the display, did you change that by accident?
I have the same problem. This was before and after the recent update. Last time I disconnected the power and restarted again, this fixed it before but now this doesn’t make it work again. No other setting have changed, I still get the cover art pop up and go away (Settings > Other Settings > Display > Turn off during playback).
Also, when I do disconnect the power and start it up again, sometimes it doesn’t boot up properly, the power on/off button just flashes slowly so I have to do it again. I’m worried that one day it will just give up and not start again. BTW, my Nova in only a few months old (December 2020).
I got a reply from NAIM support - this fixed it! (but note you will lose all your settings, favs trim, own names etc)
Put the unit into Standby, disconnect any speakers and disconnect the power cable.
Press and hold the Play/Pause and Input buttons, hold in while reconnecting the power cable.
Continue holding the buttons for 5 seconds or until the factory reset progress bar is displayed.
Release the Play/Pause and Input buttons.
Wait for the product to complete the factory reset and go into stand-by.
Press Stand-by button and the product will power up and display the welcome screen.
After completing the setup wizard, place the unit back into standby.
Reconnect the speakers.
All good second time around and didn’t lose any saved / favourites . However slight grumble, Should we have to be doing this on such expensive equipment ?