During the room booking process, if you happen to go back to verify if all the information has been entered correctly before making the required payment of €500, it is possible that the room may no longer be available as shown in the photo below:
Don't worry, the room you are interested in is currently being negotiated. The system automatically "blocks" it for the necessary time to complete the rental procedure, with a payment of €500. The blocking period lasts approximately 5 minutes, so if you find it blocked, just wait and then resume the rental procedure.