We are experiencing a server side problem with our md5 generation. Packs were uploaded, but without an md5 hash on the server, the launcher refuses to use the zip. We're working to fix the problem, but until then no packs can be updated.
Further, any packs updated since the start of the problem, approximately Wednesday morning, will not work on the launcher. They will either launcher vanilla, refuse to launch, or launch the previously installed version of the pack. The only option we can offer at the moment is to set the recommended version of your pack back to an earlier version. Please respond to your thread if you would like to do this.