HTTPS access to EmonPi?

Is there a reason that the Android App fails to work when I try to change it to use HTTPS when accessing my emonPi - I have created my own CA and certs and installed them in apache and these work fine using HTTPS (port 443) in a browser both on my PC and my Android phone (having added my CA to the underlying OS / Browser settings), but the App fails - if I revert the App to the HTTP settings (port 80) then that works, but I would rather use HTTPS.