paid search advertising is only displayed when it satisfies the search engine's criteria. The likelihood that an advertisement will rank higher increases with how well a user query matches the keywords, ad copy, and landing page. There are many different reasons why advertisements may not appear during times of high traffic. One of them is that your CPC was set too low or that your budget is too little. This can also occur as a result of a lower quality score, as advertising with lower quality scores are less likely to appear on search engine's first page of search results.