I have a subdomain multisite. I have a wildcard ssl for my site. I have been trying to figure (on and off) for months why I can upload an image in a subdomain dashboard, but none of the thumbnail images in subdomain sites show up. Some time ago, a member of this site told me I need to install a wildcard certificate to fix the issue. So I have done that. it didn't solve the problem.
In viewing the code behind the dashboard pages, I am getting 404 file not found errors. This issue is far above my level of expertise. I have enabled support access and am asking for someone to please log into the site and try to figure out what is going on. Why are the media paths not correct? Why are the thumbnail images not displaying. When you click on one of the empty thumbnail boxes, the name of the image, size, etc is displayed in popup.
For example, I upload media files for one subsite and it is Site id 81. it's media path as seen in FTP is /xxxxxxxx.com/wp-content/blogs.dir/81/files/2017/01
However, when the broken link thumbnail is clicked and the popup for that media item displays the path is shown as http://subdomain.primarydomain.com/files/2017/01/southernhens_banner.jpg
The media library path ignores the /wp-content/blogs.dir/81/ portion of the file path.
Also, I am using the Domain Mapping Plugin.
Something is altering the correct reference file path on media uploads, but the files are indeed being uploaded to the correct /wp-content/blogs.dir/blogID/year/month/ folder.