急：欧洲租车再保险问题

我准备在http://www.carhire-excess-insurance.com/网站办理租车的再保险，在填表时有提示：
Please note: if you have already commenced the car hire, we are sorry that you cannot proceed I confirm that the car hire has not started
是什么意思？是否是必须在办理租车前办理这个保险？可是我车辆已经租了，只是现在还没有出发去欧洲，还能否办理这个保险？请大家帮助。