I could not see all users to see email they have sent on specific lead potential or contact

I could not see all users to see email they have sent on specific lead potential or contact

Hi, 

We have three users in  our account, when I click on Zoho Mail Ad On Users I only see  the admin and one of the users. How do I see all users under the   Zoho Mail Ad On Users? Also when I go to lead or potential, when I go to emails, under the Dropdown  "Sent By " I only see two accounts. How do I see all emails sent by all users under this dropdown? I ahve attached a screenshot for your reference.