I found myself in the same situation as you BenSenise being Canadian and trying to get Hertz to recognize my 5 star tier status. After a month of phone calls and emails and getting nowhere I took another track. I used Twitter. And believe me I am an amateur at Twitter. I started following Hertz on Twitter then sent them a direct message explaining the problem (in less than 140 characters). They replied within an hour requesting more info and within four days and a couple more messages I had my 5 star tier status. Plus they gave me some points for all my trouble.
Regarding the CDP code go to your profile and add CDP 211762. This should then show as Platinum Card From Amex. On my profile I now have this CDP listed plus the one for EMEA. On a recent rental in California I received a 20% discount with the Platinum Card CDP. I hope to use the EMEA CDP on a rental I have planned in Europe this Summer
Happy Renting