I've updated to the latest version 2.08.4 on my android 5.1 system. The problem has improved, because now the "ok" and "cancel" buttons appear. But I still can not select whether the time is "AM" or "PM".
Attached is a screenshot.
It seems on several devices Date and Time picker dialogs don't work correct. In the new version (126.96.36.199) we've changed dialogs styles for old "spinner". I think it will solve your problem.
You can download new version from our site or from Google Play a bit later.