Using MAMP/Localhost issues

I’m trying to test out the plugin locally via MAMP and the URL is http://localhost:8888/sitename and the plugin doesn’t appear to be uploading any images to Cloudinary, yet the URL’s getting placed into a Post look to be valid URLs to my Cloudinary account.

Is it because I’m trying to do this with localhost as the URL? Thanks