User does not have the privilege to act on behalf another user error while using impersonation in Web API in Dynamics 365.

 {\r\n  \”error\”:{\r\n    \”code\”:\”\”,\”message\”:\”User does not have the privilege to act on behalf another user.\”,\”innererror\”:{\r\n      \”message\”:\”User does not have the privilege to act on behalf another user.\”,\”type\”:

Impersonation in Web API

http://www.inogic.com/blog/2016/02/impersonation-available-using-web-api-in-dynamics-crm-2016/

This error can occur in a scenario when User A is trying to impersonate User B, but user A doesn’t have “Act on Behalf of Another User” privilege.

Below article nicely explains it

https://community.dynamics.com/crm/b/magnetismsolutionscrmblog/archive/2013/07/18/act-on-behalf-of-another-user

Hope it helps..