Camunda WebApp profile shows SSO User does not exist

We use Spring Security SSO to login to Camunda WebApp. When loading WebApp dashboard, the request to /camunda/api/engine/engine/default/user/{id}/profile shows response 404 with message,

{“type”:“InvalidRequestException”,“message”:“User with id does not exist”}.

Since SSO through external IDM, the user account is not in Camuda user tables. How to deal with it?