Only 3 reasons why advertising is not working.

Often when sales are not coming as planned, the first impulse is to advertise more. While this may be the correct action, it may not always be.

As a rule of thumb - there are generally only three reasons (in my mind anyway) why advertising is not driving demand. The action required is different for each.

1. Your consumers don't know about your product / offer / solution. This is an awareness play. The action here is actually to advertise more.
2. They may be aware but don't understand your advertising. This is not about doing more advertising. In fact more of the same will do little for you. You need to tweak or change your advertising, as they don't get it. The benefit (rational or emotional) may be hidden or badly explained.
3. They don't care. In this situation, they are aware and they understand, but couldn't care less. There can be lots of reasons here - wrong audience, wrong insight, wrong product, wrong timing, no clear reason to buy, no differentiation. Your job here is to find out what will make them care. Whatever the problem is, one thing you know is that doing more advertising here won't help you much.
   

If you don't know the problem, you can't really fix it.