I’m not sure what you mean – I can see ‘terrain’ as an option in the ‘map’ dropdown where you select the map type. It still seems to be present in both the backend editor and the frontend.
Are you using a custom style? If so, those can only be applied to ‘roadmap’ maps. Google also released a new API version yesterday which seems to have a lot of internal changes (and some bugs), so it’s possibly related to that.
Sorry. I mean to have it display terrain by default. I see the checkbox option, but how can I set it to be checked by default? I seem to recall that option being somewhere in an older version of the plugin.