Go to iTunes > Preferences > Devices and check “Prevent iPods, iPhones, and iPads from syncing automatically.” This prevents background conflicts with the macOS Finder.
Find the most recent file (dated before you upgraded your macOS). download itunes 101399 for mac fixed
Under the tab, look for a notification stating that the iTunes installer was blocked. Go to iTunes > Preferences > Devices and
Alternatively, you can download iTunes 10.13.9 for Mac directly from the Apple website. Here's how: download itunes 101399 for mac fixed
If the direct Apple link is unavailable, reputable repositories like MacUpdate or the Internet Archive (Wayback Machine) host verified, MD5-checked copies of the iTunes 10.13.99 DMG package. Step 2: Overcoming the macOS Installation Block