I narrowed down the problem to line 191 of the /acf/core/controllers/post.php file:
$show = in_array( $acf['id'], $metabox_ids ) ? 1 : 0;
If I override this boolean and set it to ‘1’ for everything then the meta box shows correctly on my custom post type.
Currently the Codeblocks plugin uses the Advanced Custom Fields plugin to insert it’s meta box in the post editor.
While your method works for removing the filter to strictly post and page type posts, the more practical way to remove this filter is to remove the location array of /acf-group.php directly inside the plugin (line 16).
I will likely remove this restriction in a future release, after I have tested Codeblocks with more custom post types.
Thanks for the information.
I’m now using the plugin on a custom post type and have had no problems with its functionality.