I am having trouble with Kontact, Popup Notes in that it does not load my notes file in ~.kde/share/apps/knotes/notes.ics. Summary View does not show any notes and I cannot add notes with the New Popup Note option, ie it does nothing. In System Settings > Personal Information, I have defined Local Notes with the notes.ics Filename. Basically Popup Notes is currently totally unuseable. Previous versions of KDE worked well with Popup Notes and I have stored many notes which I frequently access. This problem results in all this information being unavailable.
For me it's fixed in 4.13.1