Sarimax endogenous and exogenous variables - Provided exogenous values are not of the appropriate shape
Check the shape of the exo variable. If you are forecasting 13 steps, then you need to provide exog variables for each of those 13 steps. The error message is saying that you only provided exog variables for 11 steps. You can either provide a larger array to the exog argument, or you can change the forecast to be for 11 steps.