This "stuck at y" in the sync status is a clear sign of a corrupted local music database file on your iPhone 14. Since you've already tried the standard sign-out/restart steps, you need to perform a deeper reset of the Music app's data. Here is the process:
1. Offload the Music App — Go to Settings > General > iPhone Storage > Music. Tap "Offload App". This removes the app but keeps your documents and settings. Then tap "Reinstall App". This often clears the specific cache file that's blocking the sync.
2. Remove the "Music" data — If offloading doesn't work, go back to Settings > General > iPhone Storage > Music and tap "Delete App". This will wipe all local music data. Restart your iPhone, then redownload Music from the App Store.
3. Toggle "Sync Library" with a delay — Go to Settings > Music and toggle "Sync Library" OFF. Leave it off for at least 15 minutes. This allows Apple's servers to "check out" your device from the active sync session. Then toggle it back ON while connected to a strong Wi-Fi network.
4. Check for a VPN or Profile interference — Go to Settings > General > VPN & Device Management. If you have any VPNs or configuration profiles active, disable them temporarily. They can often block the specific ports Apple uses for library syncing.
5. Reset Network Settings — Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. This clears all Wi-Fi passwords and Bluetooth pairings, but it also resets the network stack which can resolve persistent server connection errors.
6. Use your Mac/PC to "nudge" the sync — Connect your iPhone to your Mac via USB. Open Finder, select your iPhone, and go to the "Music" tab. Uncheck "Sync Music", click Apply, wait for the sync to finish, then re-check it and Apply again. This physical connection can sometimes bypass the wireless sync hang.
Since your iPad is syncing fine, the issue is definitely isolated to the iPhone 14's local database. One of these deeper reset steps should resolve it.
Hope this gets your library back!