Apple Music not playing purchased songs and losing previously imported songs

Sorry for the strange title. I am having some major issues with my Apple music on my new Macbook Air (15 inch version).

So for context, I do not have a subscription to Apple Music--I only use it to play music I own like I did with iTunes before. I don't stream. I either import my CDs or import mp3s I have purchased, as well as any iTunes store purchases that I download to my computer. I have my music library on an external SSD drive, and have it set to put songs there when I purchase or import them.

A few weeks ago, I noticed that Apple Music won't play recent iTunes purchases anymore. The songs show up, but when I click on them nothing happens. I can delete them from my library, and then redownload them and they work, but once I shut down Apple Music, the next time I open it up they won't play again. It is only happening in the more recent purchases--ones I bought like 4 months or so ago are fine for the most part. When I click on the individual song file info, it doesn't show it being in the external drive in the Music folder--instead it shows the location as "HD Macintosh", but it is nowhere in the HD when I look for it.

Then last week, I had the Mac OS update (can't think of the version at the moment). Since then, my library got screwed up and I had to re-import it into Apple Music. Now, a ton of songs/albums that I had put in my library also won't play. The songs "look" like they are there, but when I click on them, nothing happens. And again, if I look at the file info, it shows them as being in the HD Macintosh folder, which they aren't.

Some I have been able to re-add and they seem to work, but there are a bunch that won't. As far as I can tell the files are fine (they play in Windows Media Player on my work PC). Again, sometimes I can re-add them and they work initially, but once I shut down and then re-open Apple Music, they won't play anymore.

Apologies for the long post, but I am finding nothing online that helps with this problem. This is strictly an issue on my Macbook--if I transfer the songs to my iPhone, they seem to play fine.

Any thoughts on what could be happening? I am starting to lose my mind trying to solve this problem.