iTunes sees only songs obtained from Apple Store
I'm having difficulty setting up my iTunes music library on a new Windows 10 computer. Specifically, iTunes does not "see" all the songs in my iTunes Media folder. Apparently it sees only music I obtained from the Apple Store.
My iTunes Media folder is large, so I have it on an external drive. When I installed iTunes v12.11.13.17 to my new Windows 10 computer, I designated that external drive as my iTunes Media folder location. In the iTunes Library view, however, iTunes now seems to list ONLY the songs I'd downloaded from the Apple Store. NONE of the songs that I'd copied from my CD library (or that I bought from other sources) appear in the Library list. The songs that do appear have a cloud icon with a downward arrow. Those icons appear in the second column.
How can I get iTunes to recognize all the items in the iTunes Media folder on my external drive?
Windows, Windows 10