“Unknown availability” is show for dates for which there is no pricing information. You probably have a tariff with date ranges and need to extend your tariff into the future. You can easily do this by clicking on the “PROPERTIES” button at the top of your Dashboard and then the “Tariffs” tab below. If necessary, choose the tariff that needs to be extended, then click on the “Add a new date range” link towards the bottom of the page and add new pricing information.