Before ads can run on Facebook or Instagram, they go through a review process within Meta to ensure all of the components of your ad (images, video, text, targeting information, and ad destination) are in line with Meta’s advertising policy principles. If your FB ad is denied, it is likely due to a violation of Meta’s Advertising Standards. You should receive an email notification where you can find the reason for the denial. Once you’ve reviewed their notice, you can decide to either edit your ad, create a new one, or request a second review of your ad if you believe it was incorrectly denied. Read more on troubleshooting a rejected ad from Meta.