Check the regulator on top of the cylinders to see if they are red. If they are red, you will need to order a new cylinder. If both cylinders are empty, and an urgent delivery is required there will be an extra charge of $80 - $180.
If the regulator indicates there’s still gas in a least one of the cylinders, check for basic errors such as a pilot light having gone out. If you’re still not sure, call a registered gas fitter to check your appliances.