WWE.com's servers are overwhelmed with the demand of the WWE Network and as a result, users just aren't able to signup right now. I tried myself and got a dreaded white screen. The company released the following statement:
WWE NETWORK EXPERIENCING HIGH DEMAND
Please be patient if you’re ordering WWE Network as we’re experiencing extremely high demand. Your order will be processed as soon as possible.
The good news in all this is that I've been watching the live feed since it started at 9 AM EST and haven't had one issue, including being able to access DVR type functionality.