It’s worthwhile reading small( or non existent) print.
Just taken car of from Madrid airport.
I usually use my Amex for car rental insurance extras. no, not allowed. You either have to pay the additional insurance to them - an Extra €200 or, a deposit of €3000 and use that to cover any damage.
The next time you look for good deals; better go to trusted companies Hertz : Avis etc.
It would have been cheaper and no nonsense