We have received a number of reports indicating a popup error message shows up in the WordPress mobile app for iOS and Android users. This error indicates 'certificate issues' when a user attempts to click “View Site” in the Reader in the app.
Our mobile developers are aware of this issue and are trying to figure out what is happening. This appears to be happening to users who are running the WordPress app version 4.0 on an iPhone or iPad as well as in Android versions.
When we have any updates on this issue, we will post in this thread and let you know.