Always backup your database and site files before installing any theme, and perform all tests on a staging site before applying changes to production.
Theme missing from admin design configuration listCause: Wrong upload directory, incomplete package upload or missing theme.xml file.Fix: Confirm theme files are placed inside app/design/frontend/[VendorName]/[ThemeName]/. Verify theme.xml exists in the theme folder. Re-upload missing files, run php bin/magento setup:upgrade then flush cache.
Broken frontend…