The Activity Timeline is a standard Lightning component that displays open tasks, upcoming events, and past activities (like logged calls or sent emails) in a chronological view. If this timeline is missing from an Account page, it is usually because the component has been removed from the Lightning Record Page layout. To fix this, the Platform Administrator should open the Account record in the Lightning App Builder. From the list of standard components on the left, the admin must drag the Activities component onto the page canvas—typically in the right-hand column or a dedicated tab. Once the page is saved and activated, the timeline will be visible to users. Visibility of the timeline is a layout configuration, not a specific "Edit access" permission (Option B). Running a report (Option C) might confirm if data exists, but it won't fix the UI issue. There is no "button" for the Activity Timeline in the Object Manager (Option D); it is managed strictly as a component within the App Builder.