Where to put in Credit card details when viewing car hire booking with hertz.?

Please enter your confirmation details

Confirmation Number:

Last Name:

This is what comes up when I try to view my booking with hertz.so I put in the confirmation number and the last name,and this comes back at me.

Please enter a valid expiration date for your credit card. [xxxx]

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Yet there is no where available to do so.
Any ideas?