Related issue to this topic (and the reason I've previously had 'orphan' reservations) - I found again today that vehicle availability/pricing was totally different when logged in vs not logged in, with a much better price available when I was not logged in.

My workaround to still get it in my account (Gold Service, etc.) was to proceed to the payment page, then open another browser tab, log into my Hertz account, then go back to the booking page and hit refresh - it retained my car selection (and the price) but now pre-populated all my details and it was eligible for Gold Counter service.

So annoying to have to do this but at least a workaround!