你的同事正在行動版網站、行動應用程式和電腦版網站等多種平台放送廣告活動。他們查看廣告活動時，發現系統未顯示行動平台專屬指標。 請問這個錯誤的可能原因為何？

The correct answer is that they omitted the mobile reporting dimension in the Report Builder. To see mobile-specific metrics, a mobile dimension (like "Device Type," "Operating System," or "Mobile Carrier") must be explicitly included in the report configuration. Without it, the report will aggregate data across all platforms or only show non-mobile-specific metrics. "They only set 'Mobile App Installs' as a filter" is incorrect because a filter restricts data; it doesn't add a dimension to break down data by mobile platform. "They omitted 'Mobile Website' from the campaign" is incorrect because the question states the campaign runs on mobile websites, implying it's included. "They only set 'Mobile App' as a platform filter" is incorrect because, like the first incorrect option, a filter limits the data shown, rather than providing the necessary dimension to display mobile-specific metrics alongside other platforms.