Wordpress Opt-in forms are not showing up in campaigns

I’m using the official WordPress Opt-in plug in. When I go into my campaign in the manager and double-click to configure the Opt-in, only 2 of the 5 created forms on my website show up in the drop-down list.
Is there a limitation to how many forms can be live at once? If not, how do I see all of my created forms?