Bugs reported in the KDE Forums https://forum.kde.org/viewtopic.php?f=229&t=138128&p=369598#p369598: When KAlarm is run the first time, the calendar files are created read-only. Creating new calendar files via the GUI results works, but they are initially disabled.
Calendar files being created read-only was probably fixed in version 2.11.10, which fixed default calendar files not being created on first run.
See Bug 362962 for the read-only creation bug report.
I can't reproduce calendar files being created disabled, so closing.