When you start a home charging session, it is temporarily treated as a public session. This is because the system only recognises it as a home charging session once the session ends and the full charging record is received. At that point, the cost is automatically reset to €0. This is completely normal.
The €0 means the session has been correctly identified as a home charging session and not as a public session. Your reimbursement will be processed via payroll instead. You can track the status of each session in your Mbrella account under Profile → My Expenses → Home Charging.