Person account may not display all activity records after lead conversion

This article explains why a converted Lead's activities may not appear in a Person Account's Activity History related list, and how to make them visible again.

Steps to Reproduce This Behavior

1. Log in as a System Administrator User or another User with the needed profile permissions.
2. Enable Shared Activities.
3. Disable Roll Up of Activities to a Contact's Primary Account.
4. Enable Person Accounts.
5. Edit the Lead layout to make the Company field optional.
6. Create a Lead without a value in the Company field.
7. Create a new Task associated with the Lead.
8. Convert the Lead and select "Don't create an opportunity upon conversion."

After completing these steps, the Task is not visible under the Person Account's Activity History.

Resolution

Enable Roll Up of Activities to a Contact's Primary Account, then edit or update the activities that are not visible in the Activity History related list. For example, perform an edit and save, or close the Task.