Same wifi network?
Does your smartphone does have wifi connection?
Appears it in the naim app, but no connection to the music? So you can’t hear anything?
Pull out the mains (230V) for 1 minute. Then put it back. The NDX2 will start up. Then (maybe) it wil work again.
I have two other streamers here, and they are working with and without cable. The router is close even if my internet speed now is slow on the iPad now, but is sufficient for audio.
Could be a damaged Wi-Fi card on the NDX, stupid I never tried this before.
The flash made me notice I have to clean the dust.
If the ethernet cable is connected, wifi won’t work. The aerials must be vertical and not horizontal. I’d turn the NDX2 off by unplugging it, remove the ethernet, put the aerials vertical, turn it on again and the wifi should work.
As mentioned by Mike above, arrange the leads so they don’t strain the sockets - the ethernet particularly looks as though the cable is twisting the socket, which may break it.
Also, besides HH’s points, before you start thinking about trying to reinstall the firmware, which you would need Naim’s help to do, you could try a factory reset. I forget how you do this on the NDX2 but Google will tell you or no doubt someone else will come along with the answer in a moment.