What prob happened is you uploaded the incorrect plugin directory structure.
Make sure that the folder you uploaded has the “pluginsname.php” in its root. Sometimes when you un-archive a downloaded plugin, you can mistakenly unarc it in a top level folder named after the plugin which contains the folder you actually need to upload.
Does that make sense?
Some, or maybe all plugins that are just one file don’t even need a folder, like the hello dolly.
– whatever files or folders it requires
Another problem could be it is a bad plug in.
I like to refer to this to make sure all is cool.