Hi, everyone! Since misery loves company, I'm glad to know that I'm not the only one experiencing this problem right now. 😅 I've gone through the thread, and it looks like my experience is the same.
iTunes Match was working fine for me until today. For the past several days, I've been adding or replacing my J-Pop tracks from CDs. [Basically re-encoding them.]
So what I'd do is, if my previous track was of inferior quality, I'd remove it from my Cloud Music Library using my iPhone, then replace the file on my MacBook by ripping it from the CD [as AAC or Apple Lossless], then add it back to my Cloud Music Library. That's been working for me the past several days, until today.
I saw that one J-Pop album I have synced [as uploaded tracks] was finally out on Apple Music. That meant that if I forced iTunes Match to match that album again, the chances of matching were greater. So I removed the album from my Cloud Music Library and added it back. Big mistake, given the current situation.
Currently only one track from the 11-track album has been matched. The rest still have the "Waiting…" status.
So I think the theory about this affecting only matched tracks seems to be true. Because, until this album, all my tracks didn't match and had to be uploaded. This entire album seems like it matched, so maybe that's why it's taking forever.
It's worth noting that the tracks in the album are all in Apple Lossless, but I've never had a problem with matching Apple Lossless tracks before.