Here's how you can fix it.
Ideally, the attribute mapping should look like this:
If you cannot find the Target Attribute name "urn:ietf:params:scim:schemas:extension:enterprise:2.0:User:manager", you might have to create it by clicking on the "Show advanced options" at the bottom of the Attribute Mapping table and choosing "Edit Attribute List for Freshservice".
Then, specify
1. urn:ietf:params:scim:schemas:extension:enterprise:2.0:User:manager as the attribute name
2. Set the type as Reference
3. Choose the Reference Object (last column) as "urn:ietf:params:scim:schemas:extension:enterprise:2.0:User" such that it looks like the following.
4. Save the Attribute list
5. Establish the mapping on the previous page, where Source Attribute will be "manager" and the Target Attribute will be the field you just created, such that it looks like:
6. Save the mapping.
7. Test by provisioning a manager first and a direct report next via Provision on Demand.