There were various reports about issues with registering and logging in:
I try to create a new account (with email), but i can’t. The button is disabled.
Michael Hrenka
You need to have 3 green check marks (by entering the data in all required
fields properly) in the sign up screen. Only then the sign up button is
activated.
Or you could try out the Facebook sign up.
Reply
OK. Solved! The problem is with the password. If I copy/paste the passord, the green check mark fails. Thanks!
Michael Hrenka
Interesting.
Another user also had password related problems. Entering the password
again manually always seems to help with that.
I’ve also got informed that the Discourse forum on discourse.org also suffers from password related login issues. There seems to be some kind of bug in the Discourse software. 
Anyway, try working around this issue like described above. If that doesn’t work, please send me a mail to radivis@radivis.com about what you’ve done and what’s still now working. Thanks.