There's a number of reasons a title you expect to see in your Unsub dashboard may be missing. Those reasons include:
The journal has changed to a new publisher different from the publisher you're modeling.
The journal has changed to completely open access; in which case, including it in title by title modeling no longer makes sense.
The journal has stopped publishing articles.
Your Unsub package is missing a title price (a-la-carte price) for the journal. See here to correct this.