more than likely there’s a php error in it, I don’t test code I post here. I don’t see any errors but that does not mean I didn’t make a mistake. Try turning on wp debugging so you can see the real error https://codex.wordpress.org/WP_DEBUG
and now that I said that I see the error, I typed ‘add_fitler’ instead of ‘add_filter’, but you should still have debugging on when doing dev work.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users