3578240 - [BR] Error Message: "CM-06: The server cannot or will not process the request due to something that is perceived to be a client error. [\{0\}]"

Customer is trying to use FSM webhook to create users. When executing the BR, they have met the following error:
Error while calling [PUT https://cluster.fsm.cloud.sap/api/user/v1/users/userId?account=Account Name&company=Company Name]: 400 Bad Request: "{"error":"CM-06","message":"CM-06: The server cannot or will not process the request due to something that is perceived to be a client error. [\{0\}]","values":[],"id":"xxxxxxxxxxxxxxxxxxxxxxxxxx"

"Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental." 

SAP Field Service Management

User API, policy group, create users, error CM-02, additional comma , KBA , CEC-SRV-FSM-BR , FSM Business Rules , CEC-SRV-FSM-API , FSM API , Known Error