Matchmaking was only open so many hours in a day. I don't know if the available uptime was region based, but at least in North America, it was open in the late afternoon/early evenings Monday through Friday. It was open for most of the day on Saturday and Sunday.

It's VERY MUCH a work in progress. Despite how many people are already playing it, they're actively changing it all the time, and patches can and will drop without any warning.