If you still can't add music to iTunes after converting it to the correct format, try these solutions:
1. Turn off "iCloud Music Library"
If this option is on, you can't drag music into iTunes. Just open iTunes on your PC, go to "Edit" > "Preferences", and then uncheck iCloud Music Library.
⚠️ Important: You should back up your music library first because turning off Sync Library will remove tracks already synced to your device.
2. Turn on "Manually manage music and videos"
If you're trying to drag files to sync to your device but fail, ensure you've enabled manual management in iTunes. Once your device is connected to your computer, open iTunes, click the device button, then click "Summary". In Options, select "Manually manage music and videos" and click "Apply".
3. Update iTunes
With iTunes in extremely old versions, it's a frequent problem that you can't add songs to iTunes. You can open iTunes > "Help" > "Check for Updates" to get the latest version.
4. Unblock Songs
Rare as it might be, it happens. If your music file was obtained from the internet or another computer, it might be blocked so you can't add it to iTunes properly. You can try unblocking it by right-clicking on the file, selecting "Properties", and checking the box before "Unblock" under the "General" tab.
5. Repair Corrupt Songs
You won't be able to add music to iTunes or any other player if the music file is corrupt. You have to re-download the music or use a repair tool to try to fix the file.
🔔 If the music is DRM-protected, iTunes will not let you add it. DRM-protected files can only be opened by authorized native apps.