You can try disabling Enable Enterprise Plus features under the Query insights part of the instance settings and check whether you are able to access query insights. Also ensure that your project has the following roles:

• roles/databaseinsights.monitoringViewer

• roles/cloudsql.viewer

• roles/cloudsql.editor

• roles/cloudsql.admin

If the issue still persists, consider filing a bug issue so that the engineering team can look into it. Note that there’s no specific timeline when the fix will be available.