Not getting "Watchlisted Shows on Tonight" notification emails

In the account section for IMDb Subscription Emails and Newsletters, I checked this a week ago:

Watchlisted Shows on Tonight - When a show from your Watchlist is airing, we will send you a short message.

I have never gotten a single notification, although several of the shows I Watchlisted have been on since then. Does this just not work, or is there some other hidden setting that needs to be fixed before it works?