What is the correct protocol for when I have a question that has been previously asked by someone else? The case in point is the resolution that previous questioner received (or worked out) does not solve my issue. Should I open a new thread with the question or re-open the existing one?
There should only be a question in the very first post. So the answer is that you should always start a new thread. Add a link to the other thread in your post.
Not a requirement, but I would also recommend starting the post by saying that you saw the other thread, which had the same question, but the solution didn't solve things for you. (And link to it.)