Wpautop in wp_editor not working

Normally, the wpautop filter is only applied to the_content and the_excerpt. In this case you want to apply it to metadata. So you’ll have to add the filter.

If you look at get_post_meta, you’ll see that it is just a wrapper for get_metadata. So it doesn’t matter which one you use if you retrieve the content of the metabox. Unfortunately there is no filter call in there that you can use to modify what it returns.

So, that leaves you with the possibility to modify the metabox content after is has been retrieved. In stead of echo get_post_meta ($post_ID, $metabox_name) you would write echo wpautop (get_post_meta ($post_ID, $metabox_name))