Are you setting the post_id argument when calling acf_form() https://www.advancedcustomfields.com/resources/acf_form/. If you want to display the fields values for a current post then ACF needs to know what post to use. If you’re not in “The Loop”, as suggested by @pixelbart, then ACF has no way of knowing what post values to display and it is assuming that you’re creating a new post.
