This could be because of a few reasons.
- The users visiting your website might have ad blocking software on their browser that prevents the ad from showing.
- You don’t have, or don’t have a correctly formatted ads.txt file in the root directory of your site.
- Your pages might not yet be indexed by Google and as a result your viewers are not actually getting ads on the pages they are visiting. Google relies on the pages being indexed so they know that when they sell an advertiser space that it’s in proper context and further that it’s not a topic the advertiser might not want to be associated with.
- The hits might be from a search engine crawler. You might inspect the IP addresses of the counts to determine if this is the case. If you use the free Cloudflare services for caching and denial of service protection they will also tell you how often the webcrawlers are hitting your site.
Note: If your site isn’t fully indexed then the best thing you can do is wait, work on getting links back to your site and improving your page rank through good content. It won’t happen overnight but with work can become viable.