The game was officially released on August 28th. That's 542 hours 23 mins before the time of your post. You have played 300+ hours. That means you have spent more than 55% of the total available time in your life playing this game since launch. Hoping you had at least 6 hours of daily sleep, you ended up playing nearly 75% of the every waking hour of your life in last 3 weeks or so.
I think the game got bored of you and decided not to offer you any more fun till you take some rest and help yourself in the process.
I say that jokingly. But, in all honesty, the impact of sitting on your butt 75% of the day will take heavy toll on your body. It does not matter how old you are. You will have serious issues with your health if you don't take a break now.