@tiger217 are you trying to display it on a page template setup for the Custom Post Type? For example, if you created a Portfolio CPT (portfolio), are you using a single-portfolio.php page template?
Otherwise, if you are doing it from a different template, you will need to identify that in your get_field()
Reference: https://www.advancedcustomfields.com/resources/get_field/#get-a-value-from-different-objects
