WP uses default attachment.php instead of mine

My theme uses a custom attachment.php file, but on the production site WordPress applies the default attachment.php file, which should not exist on prod.

https://www.metlifeyourlife.com/home-care/landscaping-to-keep-you-safe/attachment/father-and-daughter-8-9-years-preparing-to-plant-tree-in-front-of-house/

vs the same thing on dev:

https://dev.metlifeyourlife.com/home-care/landscaping-to-keep-you-safe/attachment/father-and-daughter-8-9-years-preparing-to-plant-tree-in-front-of-house/

IT insists the code on prod is the same as dev, and I’ve confirmed there is no “mime-type”.php file in the theme that could override it. Am I missing something, like a setting in the wp-admin?