If you just downgraded iTunes to a previous version on your PC, you can run into the old iTunes cannot read iTunes Library.itl file error.
The iTunes library file is a database iTunes uses to organize your music and other media content. When you delete the current iTunes installation from your Windows computer, its library file won’t be deleted at the same time. It stays in the home folder of your iTunes music. What is iTunes library.itl file location or folder? It is usually found at C:/your username/Music/Tunes/ in Windows OS.
You can fix the iTunes Library.itl cannot be read because it was created by a newer version of iTunes error by renaming the existing iTunes Library.itl file to something like iTunes Library Old.itl, or iTunes Library backup.itl, etc. Then run the old version of iTunes on your PC, iTunes can then automatically create a new iTunes Library.itl file. Or you can use a previous iTunes library file. Also in the same folder with iTunes Library.itl file, you should see the ‘Previous iTunes Libraries’ folder. Open this folder, you may find different iTunes Library backup files. Copy the most recent copy of the iTunes library file, and paste it to the iTunes music primary folder, then rename it to iTunes Library.itl. After that go to start iTunes again. If the most recent iTunes Library file doesn’t work, try the second most recent copy until you find the one works.