You’ve downloaded a copy of your plugin and it does not end up as a .zip archive file?
This can happen in some browsers (like Safari) that have been set to automatically open any downloaded files. The easiest way to resolve this, is to select all the folder contents and make them an archive again.
In the video below we give you the example for the free version of WP Recipe Maker. You’d name it wp-recipe-maker.zip in that example. For other plugin files, make sure to use the same name as the folder: wp-recipe-maker-premium.zip, wp-ultimate-post-grid-premium.zip, …
Another option is to use a different browser (like Chrome) that does not automatically extract the original zip archive.