I had to change my password recently, on my laptop, which booted me off the site on both work and personal phones. When I click to sign in in either phone, it flounders around and goes back to where I was, not signed in. Weird.
I had the problem for a little while, but now it is working. It seems like once in a while rivals has a little bit of indigestion. Usually if you wait a little while it will start working. Also try closing your browser and re-opening at once or twice.