I just finished creating many custom post type plugins for our humble New Leaf Journal (more news on this to come in the near future). I wrote the php file for each plugin and then put that file in a folder.  I then uploaded the folders to our plugins directory on our web server.  I only had an issue with one plugin — my new Newsletter Leaf Journal custom post type.  For whatever reason, I could not upload the folder.  I changed the name so that it no longer had the word “newsletter” in the title and it worked.  Interesting.  (I also remembered to flush our rewrite rules.) What’s more, the plugin itself (the php file in the folder) had newsletter in the title, but my server only rejected the folder.  I do use Cloudron — could that have been the issue?