This came up last year, but it seems that the Auto-matching service for Google Music uploading is down again. I tried uploading 22 albums yesterday and not a single song was matched. Same thing happened today. These were all FLAC files which generally have a much higher match rate. They were also fairly popular artists like The Weeknd & Radiohead.
I guess I will have to try again after a couple of days. Last year it took at least 3 days to get it running again.