You appear to have the scoreText reference set correctly in the inspector, but then you replace in PlayerScript.Start() by assigning the return value of GetComponent() to it. There’s no reason to do that, and it probably returns a null value because I doubt that your player game object has a Text component attached to it. (That’s what GetComponent() does, it looks for a component of the specified type on the same game object that the current script is attached to. There’s an implicit “this.” before GetComponent; it’s being called on “this”. If you explicitly wanted to search on a different game object, you’d do otherInstance.GetComponent().)
Also, use code tags to help format your posts in the future; it’ll help with clarity. I would also highly recommend taking time to learn how to use the debugger to place breakpoints and inspect the value of variables at different moments of execution. It might take a bit of effort to get used to it, but it is one of the most valuable tools at a programmer’s disposal, and the effort is absolutely worthwhile.