If your ad's not receiving impressions or as many impressions as you expected, here are a few things to check:
Is your budget too low?
When the budget is too low for the size of your audience, it can make it hard for your ads to compete with other advertisers who can spend more money to reach the same audience. As a result, your ad may reach fewer people than we predict.
Is your audience too small?
The size of your target audiences plays a factor in how often your ads are delivered. If your audiences are too narrow or specific, Facebook will not have optimal opportunities to reach your target audience. We recommend a minimum audience size of 10,000 people and encourage users to create audiences that are 500,000 to 1,000,000.
Is your ad relevant to your audience?
Facebook will prioritize ad delivery based on the relevance of an ad to its target audience. They do this by giving your ad a relevancy score. Your relevancy score is on a scale from 1 - 10. The higher your score, the more your ad will be delivered.