I ran into this a while back and I think my browser needed a update. I usually got past by opening the browser from the cryengine launcher and it loged me in.

I use chrome all the time but I did just try with IE explorer with no problems. So I am not really sure, could it be something with your firewall settings or some kind of pop up blocker/virus scan? Just brainstorming, good luck.

Hello, If you have issues with login / redirection or similar, please contact to our support, they will rise issue for developers, so we will be aware. I hope after last few updates all become more stable
Thanks!