Issues with custom post types and sage custom templates

I’ve been working with sage which seems great so far, and I have encountered this line in the documentation:

Copy index.php to archive-gallery.php for customizing the archive page for a custom post type registered as gallery

However when I do this nothing happens, and the page does not use my template. I’ve also flushed my permalink settings by changing them and changing them back, and ‘set archive’ to true in CPT UI settings.

My custom post type is located at http://server.dev/archive/trips/some-trip
The post type slug is trips
My custom page is in the root and called archive-trips.php

Can anyone help me out with this? Thanks.

Did you set up a rewrite for the CPT to point to server.dev/archive/trips rather than server.dev/trips like it would be by default?