There might be several reasons why you are not getting the traffic you expected. You need to look at the stats to figure out why.
If you get very few impressions it is because your price is to low in relation to the quality of your content (the CTR (click-through-rate) is too low).
If you get a very low CTR, you need to improve the attractiveness of your ad. Make the headline and/or image more click-enticing.
If you don't want to change the ad, you have to increase the price. That way the ad will be more competitive and get more impressions/clicks.
It might also be that you have narrowed the targeting too much. Opening up for a larger audience will of course allow for more traffic.