It depends on the type of reservation you have. Most European rental car reservations include some type of CDW insurance. If you want to use your Chase Sapphire insurance (I have the same card), you need to make sure you don't have ANY CDW insurance included in your reservation. The drawback using your Chase Sapphire may be the car rental company requiring an authorization on your car for the full value of your rental car. It may be even around 30,000 EUR or more so make sure you have enough funds available on your card for this hold authorization.