Issue: Unable to see the field tracking for the last 18 months, for example, Installed Product History.

Resolution: You can select certain fields to track and display the field history in the History-related list of an object. When Field Audit Trail is not enabled, field history data is retained for up to 18 months and 24 months through the API. If the feature Field Audit Trail is enabled, the data is retained until you manually delete it. Be mindful that the time limit for tracking history differs between history tracking and field audit trail. To enable the feature, raise a request with support.

For more information, see Field History Tracking.