I have a question which has already been asked by someone else in a previous post. An answer was given in that post (by @Tim Malone), and I have attempted to implement it. But it is not working as expected. I'd like to ask for troubleshooting tips, but I'm not sure if I should continue that question, or start a new one, ensuring I reference the previous question. How should I proceed?
Often you could comment on the answer post to say you'd tried the same thing and it didn't work (and include what did happen), and the author of the answer (or anyone else who comes across it) may be able to help out. There may even be another use case that could be edited into the answer by the answerer, to help both you and future visitors.
However, given you don't have 50 rep yet, you're unable to comment on other people's question threads, so you've done the right thing in coming here to ask what the best course of action is.
What you could do really depends on the problem you're having:
If you're getting errors, start by searching for those particular errors - the cause may not be directly related to the filter discussed in that answer; it may be caused by something else, and by digging into the error messages you might be able to solve it on your own.
If you think it might be pretty simple for someone here to solve, you could try jumping in to chat - you can ask pretty much whatever you want there, and it works well for really quick questions :)
Consider whether the question asked in the post is the only way to solve the larger problem you're working on. It's probably unlikely with a straight-forward question such as this, but often your exact problem won't be the exact problem someone else is solving, and there may be many ways to achieve your end goal (in other words, be sure you're searching about your problem, not just about one solution to it - see XY problem for more info)
Or, post a new question :). To avoid your new question being closed as a duplicate, all you need to do is explain what you want to achieve, what you did (i.e. you tried what was in another answer), what result you got, and what you've tried from there. Tell us where you're stuck, and most likely someone can help. If it's a common problem it may even end up being useful for someone to link to your question from the original answer to help others find it too.
I think it depends what you mean by "not working as expected". If it's a similar question and you're not receiving the expected output and are wondering why then it is acceptable to link back to the original question, state what you've tried, what isn't working, and what you've done in attempt to solve the issue.
Typically, questions asking how to fix PHP errors such as:
Notice: Undefined variable: release_author in B:\oblo\blaw\wp-content\themes\my-theme\functions.php on line 9
Or functions not being found etc. are closed as too localized and should be dealt with by general debugging.