I was able to open the launcher, but now it just says "Checking for updates... " What do I do?
This usually means that the game servers are down. You should receive an ‘Unable to connect to server’ message after a short time of trying to connect.
If the server is down for maintenance, it will be posted in the forums with a rough estimate of when they will be back up. If there is no announcement at all, the server may have crashed. Please be patient and wait for the servers to be brought back up. If the problem is severe enough that it will take some time to get fixed, Cyan will post an announcement with more information.
If you have been getting this message for some time, and you do not see any mention of server trouble on the forums, please feel free to contact support for more information.