enter image description hereI am getting negative values while using FB Prophet model even when I set the growth to ‘Logistic’

df_Employee_Service = df[df['Operator Name'] == parameters['Operator_Name']]
df_Employee_Service = df_Employee_Service[['Ticket Issue Date', 'Ticket Id']]
df_Employee_Service = df_Employee_Service.groupby('Ticket Issue Date').count().reset_index()
df_Employee_Service['Ticket Issue Date'] = pd.to_datetime(df_Employee_Service['Ticket Issue Date'], format='%d/%m/%Y')
df_Employee_Service.columns = ['Date', 'Number of Tickets']
df_Employee_Service = remove_outliers(df_Employee_Service, 'Number of Tickets')
df_Employee_Service['cap'] = df_Employee_Service['Number of Tickets'].max() * 1.2  
model = Prophet(growth='logistic')

model = Prophet(growth='logistic')
model.fit(df_prophet)

future = model.make_future_dataframe(periods=int(parameters['Forecasting_Days']), freq='D')
future['cap'] = df_prophet['cap'].max()
forecast = model.predict(future)
print(forecast[['ds', 'yhat', 'yhat_lower', 'yhat_upper']].tail(20))

fig, ax = plt.subplots(figsize=(12, 6))
model.plot(forecast, ax=ax)
plt.xlabel('Date')
plt.ylabel('Number of Tickets served')
plt.title('Forecasted Number of Tickets served by ' + parameters['Operator_Name'])
plt.legend(['Actual', 'Forecasted'])
plt.show()

What seems to be the problem?

I try changing seasonality but nothing changed.