Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Apple Rolling Out iTunes Match Internationally (UK, Europe , NZ & AUS)
Apple seems to be rolling out iTunes Match around the world this evening. This has not been officially announced by Apple and reflects in the glitches in the service , this could be because of a mistake or a partial roll out.
iTunes Match in the UK costs ?21.99 for a years subscriptions , in Australia the service costs A$ 34.99 and €24.99 in other parts of Europe.
People are being able to sign up for the service and are receiving confirmation emails from Apple but the service is not function-able at this minute. If you want to sign up for iTunes match you can try this direct link HERE which will open the correct page in iTunes.