Songs grayed out on Apple Music

I have older music (from Itunes days) plus recent additions since from Apple Music. At first glance, all the older stuff seems to have synced to my Music App on my PC (windows) yet a lot of the songs are grayed out so while they are listed, I can't click on them to play. However, they are all working on my IPhone. How can I get them to work on the PC? I pulled up my old Itunes and when I click on those grayed out songs in Itunes, it says file not found. Almost all the music was downloaded from CDs I had back in the day. I thought that was the issue (ie not purchased from Apple music) but that's not the case. In fact, there's an album where some songs work and some are grayed out. Very frustrating. A second issue that occurred a long time ago during some device update is that albums I created have disappeared and the songs are just listed under the artist or song name. I know I can create a playlist for said album but just curious what might have happened.