iTunes on Windows Desktop shows songs as being on phone but they are not
I have an iPhone XS and a Windows 10 desktop. All OS and Apps are the latest versions.
I recently did a synch to my phone to (hopefully) add some new tunes. What happened, instead, is that most of my music is no longer on my phone. iTunes desktop shows 4000+ tunes available on my phone. In reality, the only ones there are ones I've purchased from the iTunes store.
After several attempts at resynching, re-authorizing the computer and other things, I decided to create a new clean iTunes library on my desktop. With my iTunes library now empty, I synched the phone again. Same result - the only tunes there are ones I've purchased. But iTunes desktop still shows the 4000+ songs there.
Help?