We have subdomain websites as well, the main - called Dewalist.com.
We already set up Google Adsense, and working well with the main site and one of the subdomains. But it didn’t work with this website: ask.dewalist.com, where the Discourse web app is.
We already configured the Adsense Publisher code and the ad unit.
It came up with ADVERTISING text, but no advertising showed up. We checked the view source code, which has the right PUB and ad unit id.
Content Security Policy: The page’s settings blocked the loading of a resource at https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js (“script-src”).