Before ads show up on Facebook, they’re reviewed to make sure they meet Facebooks Advertising Policies. Typically most ads are reviewed within 24 hours, although in some cases it may take longer.
What Faceook Considers:
During the ad review process, Facebook will check your ad's images, text, targeting, and positioning, in addition to the content on your ad's landing page. Your ad may not be approved if the landing page content isn't fully functional, doesn't match the product/service promoted in your ad or doesn't fully comply with our Advertising Policies.
What Happens After an Ad is Reviewed?
After your ad is reviewed, you'll receive a notification letting you know if your ad is approved. If it’s approved, Facebook will start running your ad.