I have been having this issue also recently. It doesn't work on desktops but wirks fine on my android phone. Maybe the cable companies are blocking it - I'm not sure. But yeah I was a little puzzled too.
Have you tried contacting their support team. They're pretty prompt with responding and they would most likely have A MORE credible answer for you. It works for me but I'm also using Android phone.
I would like to say that I have had a problem today with accessing P411 too, connection "times out" although connecting via mobile phone on 4G network works just, just my ISP connection doesn't seem to work. All other websites work fine through my ISP, and I've tried multiple browsers, etc.
I sent an email to support with my IP address just in case its been accidentally added to some sort of blocked list, my account is in good standing and like I said via 4G it works just fine.