There are currently problems for some users with Apples servers, which is causing Matching to stall. My advice would be to stop the process and try again later.
It is possible that you just have some problematic tracks, but I'd say it's quite unlikely. Some people have given advice about how to deal with this, if you want to have a read, but what you report is consistent with the general experience and I'd save yourself the bother if I were you.
I would report it to Apple though. The more reports that they get the better.