CPT not visible to another plugin

I'm using a theme which makes use of some CPTs. I've got a plugin which can filter and display posts and which accepts CPTs in addition to core Posts.

The plugin can see the CPTs used by the theme and makes them available for filtering and display.

I've used CustomPress to create a CPT of my own with a hierarchical taxonomy and that seems to have worked for me being able to see the CPT on my admin menu and create posts and assign them to the taxonomy.

However, the CPT created with CustomPress isn't visible to this other plugin.

Is there an option I have to tweak in CustomPress for this CPT to make it accessible by this other plugin? It's probably something obvious...