iTunes Wi-Fi Sync stopped working with iOS 11.2 Syncing from the iPhone using Settings > General > iTunes Wi-Fi Sync doesn't work (just get "searching for computer" which goes away after about 1 minute) and the device never shows up in iTunes.
I was able to get it to work by syncing once over USB. iTunes put up a "Trust this computer?" dialog as if I hadn't ever synced before. After that everything worked as before.