Who is the current owner of the website? I've stopped renting from Hertz back in 2011-12 because their reservation page was useless. Returned to Hertz because they had attractive prices for the location I was going to. It took me only 30 minutes to make 1 reservation. If their prices weren't half what competitors show, I would have gone from their web site after 2nd try.
Its embarrassing to have non functional webpage in 2019. (Mobile app was giving me the same errors while trying to book the car).