Can't log in to iMessage on El Capitan
I installed El Capitan yesterday and I can't log in to iMessage. I get the iMessage sign in box but when I enter my Apple ID and Password and hit Sign in, nothing happens. Also, every time I start up, I get a screen telling me that my iCloud password needs to be updated.
How do I get iMessage to work? and How do I make the iCloud password verification box appear every single time I log in? Any suggestions?
Running El Capitan on a MacPro 2009