If the latest PRs aren’t showing up (and those are the ones where the Quality Gate isn’t being reported to Azure DevOps)… well there you go!
Have you checked the pipeline logs of those pull requests to see why analysis wasn’t uploaded to SonarQube? Do you see the SonarQube tasks running in the context of those PRs?
Hm. Before doing that, I suggest making sure your background tasks are ever getting processed. You or an instance admin can check the global Administration > Projects > Background Tasks. If a lot of tasks are piling up and not processing, that represents another issue. If they’re just taking a long time, that’s another thing.
there are no tasks with pending status. All of them are with success status. regarding the duration it has many different times, for example for one project sometime is 36seconds other times +10min. And other projects reach times of +1h
If all your background tasks eventually get processed, then eventually your PRs should be decorated, even if it takes a while. Is that happening? If so, then the real thing we need to investigate is Compute Engine performance.