Hi,
Please check if the sha1 of the analysis matches the HEAD of the PR. This will not be the case for example if your build pipeline does a merge commit first before running SonarCloud analysis. In that case the sha1 will be different from the HEAD of the PR. And in that case decoration is skipped, because it wouldn’t be visible anyway, being a temporary local commit.
Also, when you open your PR on SonarCloud, do you see a warning in the top-right part of the UI? (a box with yellow background)