A WordPress theme installation error usually occurs due to one of the following reasons: Incorrect File Format that uploading a .zip theme file, not an extracted folder. WordPress only accepts zipped theme files. File Size Limit Some hosting providers limit the maximum upload size. If the theme is large, increase the upload size limit or install via FTP. Missing style.css File Every WordPress theme must contain a style.css file in the root folder. If it’s missing, the theme will fail to install. Theme Conflicts or Duplicates .If the same theme or version already exists, WordPress may block installation. Try deleting the old version first. Server Configuration Issues Sometimes PHP version, memory limits, or permissions cause the error. Updating your PHP or adjusting permissions can help. Uploading to the Wrong Section – Make sure you upload themes under Appearance → Themes → Add New, not under Plugins.