It appears that your new sub-directory's sessions are not being tracked accurately in Google Analytics 4 despite proper implementation. To resolve this issue, ensure that the GA4 tags are correctly placed on all pages within the /au sub-directory. Additionally, check if there are any conflicting tags or settings that might be causing the discrepancy. Review your implementation in Google Tag Manager if you're using it. Double-check the property settings in Google Analytics 4 to confirm that the correct views and filters are applied. If the problem persists, consider reaching out to Google Analytics support for further assistance.