Q: why won't my iPhone sync with iTunes?

Did you already reset the network settings on your iPhone in Settings/General/Reset?  After that all passwords for network connections have to be filled in again.

Maybe also check this article again:

Sync your iPhone, iPad and iPod touch with iTunes using Wi-Fi - Apple Support

Did you also try to set it back to factory settings, without using any backup data?

Use iTunes to restore your iOS device to factory settings - Apple Support

As a first step you could try to set it back to factory settings, to make sure that the newest firmware is downloaded, then restore from the latest backup and try again to sync via Wi-Fi.