You haven’t properly registered the taxonomy for your post type. You register your post type like this:
register_post_type( 'custom-post-type-1',
Meaning that your post type is named custom-post-type-1. But when you register the taxonomy, you’re registering it for a post type called my-menu“
register_taxonomy( 'custom-taxonomy', 'my-menu',
You need to register your taxonomy for your post type:
register_taxonomy( 'custom-taxonomy', 'custom-post-type-1',