This can be due to several different reasons as we have several requirements that need to be met for the smart charging to work. The most common reason is that you have a battery percentage in the car that is lower than 20%, because we have a barrier where we always charge the battery to at least 20% regardless of what the electricity price is. This restriction can be changed yourself in the app when you get into the car, but we recommend 20% to avoid possibly being stranded.