The ink can dry out or some contaminant can get on the ball and preventing it from rolling. What I usually do is run the ball along the sole of my shoe (or use anything that has high friction material) 9 times out of 10 it makes the pen work again.

Valve does not limit you in where your game is sold, the publisher of the game has to set this and the publisher for Helldivers 2 is PlayStation Publishing LLC.