If you have posted what you hope is a kind and helpful response, it can be upsetting to find your response is marked as "unhelpful" by the story author.
How can you respond to this?
First, don't take it personally. You responded as you thought best, but it wasn't what the author needed. That happens.
Second, rather than immediately trying again, consider responding to the author, apologising that your reply wasn't helpful and asking what what they would find more helpful at this point.
Third, it may be that an online exchange just isn't a good fit for the situation. Consider offering other channels such as a phone call or a meeting.