I've had a hard time getting plugins to show up in Sketchup. Re installed and re-zipped, restarted etc. several times with no luck.
But found out what the problme. This migth help other users with Mac.

There are TWO sub folders named Plugins.
1.) In Library/Applicaiton support/Goggle sketchup/Plugins (this is the corret folder to put your new plugins...)
2.) If you right-click (Mac) on the Sketchup program located under Applications, you can choose to "show packaged". This lets you see the subfolders "hidden" in the the application. There is a Plugins folder here as well. (Don't put your new plugins here!)

Thanks to all of you guys sharing all your knowledge and creating stunning plugins.

Best,
Lukas