Thank you for the clarification NukeThief,
Next, let's try the following steps:
1. Make sure all devices are up to date.
2. Check whether content can sync successfully via USB
3. If contents syncs via USB, make sure the computer is not connected via Ethernet (this is not supported with Wi-Fi Syncing )
4. Connect the computer and the iOS device to the exact same Wi-Fi network name
• NOTE: A 2.4GHz band typically has a different network name that the 5GHz band broadcast by the same router.
5. Power cycle the computer, iOS device and all network hardware
6. Reset Network Settings on the iOS device, forget the network on the computer, then rejoin the exact same Wi-Fi network name
You can also, check out the "Apple recommended" section in the following post:
iTunes not seeing my iPhone over Wifi
We hope this information is useful. Kind regards.