Hi. If you have a controller connected, then please check your controller. If you don't have any, then it's possible that you're in Observing mode.
If you did not select any character, you'll enter Observing mode, which manually alter your camera for tracking other player's look direction. The list of playing character is on the right, which helps you to observe a specific player. Click on Character Select for start playing, or if you want to continue observing other player, just click on Resume. In Observing mode, you can press [Space] for changing observing mode.