I had the same thing happen to me and I fixed it accidentally by editing the post and hitting PUBLISH. I got a pop up window warning me it would become public, but I hit OK and it published as normal. Try that.
When publishing any post, there is a (blue) menu to the site with many options. there is one option for page status (click the “+” … ie open that option) and change your setting from private to publish and then then upload/publish your post.