The core sense of now that is that now, in the present, one thing has been accomplished, and what follows—the “consequence”—lies ahead, in the future. But what is in the future may or may not be known; and now that is very often used in situations where it is not known.

Now that he had graduated, he was ready to look for a job. OR
Now that he had graduated, he had no idea what he would do next.

Harry's case parallels the latter: this thing is done, what is the next thing to do?

The core sense of now that is that now, in the present, one thing has been accomplished, and what follows—the “consequence”—is in operation in the present, and/or lies ahead, in the future. But what is in the future may or may not be known; and now that is very often used in situations where it is not known.

Now that he had graduated, he was ready to look for a job. OR
Now that he had graduated, he had no idea what he would do next.

Harry's case parallels the latter: this thing is done, what is the next thing to do?