FAQ - Sage Intacct: Error Adding an Employee Email Address in Sage Intacct
You have two different Employees with the same email address set up.
To resolve this, delete the duplicate employee in Sage Intacct then sync the connection in Expensify by going to Settings > Policies > Group > [Policy Name] > Connections > Sync Now.
An employee email address cannot be added in the employee listing within in Sage Intacct (there is no email field). Instead, you need to add/edit the employee email address by going to Company > Contacts and searching for the employee in the list.