Diamond are the only print distributor, but digital is nothing to do with them - therefore digital exclusive books never show up on Previews World, and have been known to only be announced on their release day, without being solicited earlier. I don't think subscriptions are done by Diamond either, don't the publishers handle that themselves?
So like I said, check marvel.com (and other publisher websites such as dccomics.com) and not Previews World.