I have a subdirectory multisite configuration. Works very nicely except I cannot get the featured image for custom post types to show up in the post add screen.
To be clear, I author themes all the time and this seems to be a problem associated with the fact this is multisite.
I register the post type as usual, add the thumbnail supports key. Everything else is taken into account (editor, custom-fields) and work, but thumbnail does not add the Featured Image block to the custom post type as it usually does for normal single site wordpress installs.
Wondering if anyone has any experience with this issue or whether I should log this as a bug.