Adding a "Zoho mail add-on" user appears to have reset all existing mails previously listed in CRM?

Adding a "Zoho mail add-on" user appears to have reset all existing mails previously listed in CRM?

I have used the Zoho mail add-on for CRM for a long time now, and I am happy to be able to see any mail correspondence with a contact in CRM just by scrolling down to the "Emails" section.
However I have recently purchased an additional license for the mail add-on because we have a new user, and after activating the new extra license all existing mail information in the CRM appears to be reset or erased or what you want to call it.
It is things like this that makes a user/administrator kind of nervous..

Please help!

Thnak you