Thanks for the responce, I've tried the file marked 4.20 within the zip and used FTP to place it into the plugnin directory, but it still refuses to show. There's no logs regarding Square not being installed correctly either, so it's very odd. The only thing it whines about is a sevenspikes plugnin, but that's to do with my theme.
Seems, it's there, it's just marked to delete instead of install. I"ll be honest my knowledge of nop is pretty limited being self taught and mainly do things on a trial and error basis, so I very much appreciate the help as I fumble my way though this!
You can as well add it to the installed list. Just duplicate one of the others change the attributes like plugin name and the version of square stated previously for nop 4.2. Assuming the square plugin folder is still in the plugins folder. Remove the the to be deleted as Yinda proposed, save and restart the application via the admin panel.