I think possibly your vehicle has multiplex wiring (does the dash tell you if a door is open or a bulb has gone?).
In which case, it is entirely possible the relay responsible for that particular circuit is either malfunctioning or the BCM is on the blink.
The BCM is Body Control Module and is a computer controller that decides which circuit gets which signal. Multiplex is great when it works, but when things go wrong, it can be a pain to figure it out.
Back in the early days, Peugeot's 406 or 407 (I forget which) had multiplex. A good few suffered a dashboard malfunction and it was a bugger to find.
Eventually, it was tracked down to the boot mounted CD player. It was mounted low down and if the boot suffered water ingress, the CD player would fill up & short out the dash.
Imagine, something 6 feet away causing problems!
Anyway, it is possible something else is causing the problem and affecting other circuits like the number plate lamps & interior light.....
Only real way to find the cause is have a look through the BCM for stored fault codes.