After seeing many repeat threads that offered solutions to downloading the missing content that was released today, I'm posting some information that has recently came from @IWMarkRubin on Twitter. In response to some people, he has said that he is also having problems with this month's content not being in the PS Store, but also his Elite subscription is missing from his PSN account, something that many people are also reporting. From the tweets, it appears that the problem is that the PSN has removed the Elite subscription status of the affected people's PSN accounts which results in being unable to download the content. IW is working with Sony in resolving this issue. Feel free to post here describing your issue so that others are aware of the situation and to anyone working for Infinity Ward or is a moderator, feel free to assist people in resolving and/or reporting this issue.

Update: @candyslexia has suggested going to the main PS Store and browsing the add ons for the DLC which has worked for most people. For those that still could not see the DLC, post here describing your situation.