How to solve "Missing stylesheet" problems when installing a WordPress theme?

1. This problem is usually happening when you are trying to install an unzipped folder(Extracted file), instead of the .zip file of your theme. You are trying to upload other than the ZIP Compressed version. Other compression formats are not supported while uploading a theme. When installing any theme in WordPress, the file should be uploaded as a .zip file.
2. Another solution: The .zip file is corrupted or incomplete. In this case, you need to download a new version of the .zip file for the theme that you're trying to install and upload it again in WordPress.