Admin template mod not showing up in production?

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I've got an admin template mod - adding extra settings to a forum as in https://xenforo.com/docs/dev/lets-build-an-add-on/#modifying-the-forum-edit-form - in an add-on and it works fine on my dev server but not on my production server.

I've used the same technique in a different add-on and that works fine on both servers
I've tried changing the find/replace text and the execution order so the values are different to the other add-on I wrote, but that also makes it work ok...