The function alone seems to be working. pgAdmin gave me the thumbs up on it, as well as the table. I tried many different ways to type the function and INSERT INTO portion. I have been working on this for over an hour and seem stuck. I was doing okay up until this portion. Any ideas?

CREATE FUNCTION rental_string (title VARCHAR(250), rating VARCHAR(250))
RETURNS VARCHAR(250)
LANGUAGE plpgsql
AS
$$
BEGIN
RETURN CONCAT(title,' - '  ,rating);
END;
$$;


INSERT INTO detailed_table 
    SELECT DISTINCT rental_string(f.title, f.rating), c.name, l.name
    FROM inventory AS i 
    JOIN film as f ON f.film_id = i.film_id
    JOIN film_category as fc ON fc.film_id = f.film_id 
    JOIN category AS c ON c.category_id = fc.category_id
    JOIN language AS l ON l.language_id = f.language_id
    GROUP BY f.title, c.name, l.name
    ORDER BY f.title;


CREATE TABLE detailed_table (
name_rating VARCHAR(250),
category VARCHAR(250),
film_language VARCHAR(250)
);

Below are the errors I keep receiving:

ERROR: function rental_string(character varying, unknown, mpaa_rating) does not exist
LINE 3: SELECT DISTINCT rental_string(title, ”, rating), c.name, l…
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.

SQL state: 42883
Character: 47