Title tag not found or duplicate
Note: If you see MANY problems under Scan Issues, see Many Scan Issues all at once?
Title tag NOT found: Often this is caused when the app's code is gone from your theme file (maybe due to a theme change). It's easy to fix: simply press the Sync and Check Theme button in the app's Settings.
Found more than one Title tag: Usually this error is caused when you have more than one SEO app installed. Uninstall other SEO apps in your Shopify admin, and that will fix the issue. Generally, having multiple SEO apps installed causes conflicts in your site's code.