I have an iPhone X that for reasons was backing up and syncing to two of my Macs at home. I wanted to stop using one of them as a destination, but this was the only computer that the iPhone recognised as a Wi-Fi Sync destination on the iPhone's settings: General > iTunes Wi-Fi Sync.
I read online that the iPhone is actually designed to only sync/backup to one computer at a time – not two as I had it. Apparently, the only way to assign which sole computer to sync to is to Erase the iPhone to factory settings and restore from backup, in which case the iPhone supposedly should greet the next connecting computer as a new computer.
Today I erased the iPhone and restored from an iTunes computer backup. I'm not sure if during the process the iPhone started to see the computer as a "new" backup destination.
Either way, I'm now having a problem where on the iPhone's General > iTunes Wi-Fi Sync, it shows the same image below regardless if I flip the checkbox in iTunes: Sync with this iPhone over Wi-Fi:
I have tried various combinations of flipping the checkbox and restarting the iPhone/iTunes/Mac and syncing the iPhone, without success. The iPhone screen constantly shows the image to connect the cable.
Since I just erased and restored the iPhone from backup, I'm a bit pessimistic it would help with the issue. I suspect something might be wrong with the unique syncing identifier for iTunes/Wi-Fi Sync?