That's because you have not installed the right theme files, the ZIP file you are trying to install has all the files and is not only the WordPress theme in it.
Go to Themeforest.net > Downloads area find Oxygen theme and choose the “Installable WordPress file only“.
Hi,
The package could not be installed. The theme is missing the style.css stylesheet.
Hi there,
That's because you have not installed the right theme files, the ZIP file you are trying to install has all the files and is not only the WordPress theme in it.
Go to Themeforest.net > Downloads area find Oxygen theme and choose the “Installable WordPress file only“.
Best regards,
Laborator Team
I have it installed. Thank you