I can’t sync my new iPhone XR to iTunes

Before trying anything else, be sure you have the latest version of iTunes on the computer. This applies to both Mac OS and Windows. Sometimes just updating to the newest version of iTunes is enough to resolve all syncing problems, particularly if the desktop software hasn’t been updated in a while. You can always download the newest version of iTunes. Update iTunes before proceeding.

then simply quit out of iTunes, then relaunch the app, and try syncing again. Sometimes this is enough to get things working again.