A lot of people have been experiencing issues accessing the WWE Network today.
If you subscribed today via WWE.com, make sure that you: a) were asked to enter your credit card information and b) you received a confirmation email.
When I signed up through WWE.com, I was receiving an error that read, "Media Error: Video not available" I actually had to click on "My Account," and then select "Buy Gift Subscription," which is where I selected the "One Week Trial" button and entered my credit card information. Upon doing that, the videos started working.
It really should be fixed to redirect you to the credit card information screen after registering. Hopefully that works for those of you experiencing that error.