This may not be the case, because we’re using the google api the way they recommend when a new ad should be added. Create the container, ask google to fill it.
That said, there are other factors at play with ads, like ad tags for the niche content of the forum and whether Adsense has enough paying line items for the slot with a blank ad that match the criteria set.
For niche forums, paying ad slots may not always be available, and thus blank ad spots appear.
Other individuals using ads outside Discourse also complain of the blank ad issue, so this isn’t entirely tied to only Discourse.
If you do have a blank ad showing on your community, I have been able to find solutions by checking my browser console for errors and acting on these errors. If there are no errors, check your Adsense dashboard for why blank ads are displaying.