In Post Ads - Ads not displaying in random order

In Post Ads - Ads not displaying in random order always showing sam ad as though there is only 1. We have tried all the settings and just can't seem to get anywhere.
In theory, we have four advertisements. It should just randomly show the advertisement. We kept it at four, since we saw no reason to add more to the ad-database. This is based on the fact that we basically ONLY show one advertisement per article (since most articles are not long enough)
For example, our most recently published article; it always will show just this ad. LINK to article: https://travelzork.com/learn-video-poker-how-to-get-started/
We have yet to see it EVER choose a different ad from the ad-database.
We tested by trying a bunch of articles. The same article a few times. Always the same ad.