Unable to create new users in Zoho CRM - "Zoho CRM ID already exists. Please use a different Zoho CRM ID."

Unable to create new users in Zoho CRM - "Zoho CRM ID already exists. Please use a different Zoho CRM ID."

I have tried to create 2 new users with emails that I know are unique.  The people I am trying to add have not used Zoho before, but I am still getting the message: "Zoho CRM ID already exists. Please use a different Zoho CRM ID."  Why would this be happening?  I have 5 licenses and just 3 in use.