Not looking good as there is an advance sign: -
https://maps.app.goo.gl/zu2KCZLWrofr3TQr7plus they've put another white text on blue sign just after it too. telling you to turn left and avoid nus lane enforcement ! Neither sign is illuminated, but are both directly under street lamps that I assume were lit when you passed this way.
Not good with you waiting so long to post here. It doesn't give us any time to investigate the council webpages for submitting representations. Even if an offence is made out, the council enforcement processes if flawed, can win an appeal on their own. Nottingham are well known as being exceptionally venal, so will probably not re-offer the discount if you submit reps now. However, have a look at their reps screen and see if all of the statutory grounds for an appeal are present. They should match what is on your PCN.
