I know this post is three years old but sharing my experience for everyone's future reference.
I had exactly the same issue and tried to figure it out for a while knowing in my heart that I entered everything I could (T4A slip and T2125). I removed the T4A and T2125 tabs from the left hand navigation pane and added fresh T4A and T2125 tabs then re-entered all the info. That cleared the error message in 'Review' tab! It looks like this is an application glitch. If you know this, it is so simple to solve the issue but if you don't it is a nightmare. Hope this helps.
