On the Discourse side it looks like things are working, but I have no insight into reasons why Google might not be serving ads.
Are there any errors or notifications in your adsense account? For new sites sometimes it can take a little while for ads to start being served.
If you’re not seeing any issues with your configuration Google does have a specific form you can submit in the case where ads aren’t appearing: https://support.google.com/adsense/contact/cant_see_ad