An issue with iTunes Match seems to have cropped up in the last few days, according to this thread posted on Apple’s Discussion boards.
The issued stems from when the user goes to use the service. The service gets “stuck” during the normal gathering process. This problem seemed to have started back in April and hasn’t let up since.
The issue is affecting both Macs and PCs.
We will continue to monitor the situation (as I need to update some stuff) and issue updates as necessary.