If your ads don’t get impressions you should try to increase your max bid. Go to “Ads”, select the ad that don’t get impressions and click “bidding” in the bottom toolbar. Make sure your bid is close to or equals the max bid. You can always update your bid by typing in the new bid and press “update”.
If you already have updated your bid, make sure you haven’t reached your spend limit on Facebook. To see or change your spend limit go to the “Billing manager” in your Facebook Ad account. Read more about ads delivery in Facebook's help documentation.