Sometimes it’s a simple IT error. A content administrator may have accidentally set permissions to "private" or "internal only" during a website migration.
The "Access Denied" error encountered when trying to access https://www.xxxx.com.au/sustainability/better appears to be due to [insert presumed cause]. Efforts to resolve the issue have [insert status]. Continuous attempts to resolve the access issue are necessary to [state the purpose, e.g., gather information for sustainability reporting].