I have no indicator icon when no alarm is set on Ubuntu Unity 16.10. Ubuntu package version is 4:16.04.3-0ubuntu2, not sure what version that is based on. Kalarm is running, but does not show an indicator icon unless and active alarm is set. Shouldn't there be at least a disabled alarm icon? Also any attempt to bring the window open via relaunching in terminal causes a crash with the message: "Message recipient disconnected from message bus without replying"
I'm not sure how indicator icons work in Ubuntu, but on some systems certain icons can be hidden by default unless they are manually shown. For example, in the KDE Plasma desktop, clicking an up-arrow icon beside the other icons brings up a list of hidden indicator icons (which can then be clicked in the same way as the non-hidden icons). There is a settings dialog which can be used to control this, so that any icon can be always displayed, always hidden or use automatically controlled visibility. KAlarm by default hides its icon when no alarms are active, so I would expect the behaviour you are seeing. The only question is how you get access to hidden icons in Ubuntu. What desktop are you using - Unity, Gnome 3 or what?
I was using Unity when I encountered the lack of an icon. I have since added a recurring alarm and the icon is now present. It just seems odd that the icon is missing entirely with no alarm set and not simply switched to a disabled alarm icon. I install Kalarm whenever I set up a clean install and usually don't set an alarm right away because I would not have yet moved over my custom alarm sounds. While most users may immediately set an alarm at first run, I imagine several users that prefer Kalarm to the various other available alarms may experience the same issue and try to resolve it before setting an alarm (as I did for nearly a day). I downgraded the importance to 'normal', but it would be nice to have this altered whenever a new update comes out.
The question is whether Unity provides an option to display hidden system tray icons. If it does, you can use that to see the icon. Alternatively, you can use KAlarm's configuration dialog to show the icon at all times. Go to the menu option Settings -> Configure KAlarm. Then select the View page, General tab, and choose "Always show" under "Show in system tray".
I am unaware of any method of viewing hidden notification in Unity. As for the "Show Icon" settings, Unity appears to not handle these as expected. I don't recall changing the setting, but it was already set to "Always Show". I tested the other settings by first disabling my only set alarm and then applying the settings, the icon remained. It wasn't until I used the "Enable Alarms" toggle that the icon disappeared, but this behavior occurred even when "Always Show" was selected. Additionally, deselecting "Show Icon" did nothing after applying the setting and the icon remained. To sum it up, the icon only appears when the "Enable Alarms" toggle is checked, but disappears whenever it is unchecked... regardless of "Show Icon" settings.
I think that KAlarm needs to set the default system tray icon visibility based on the desktop (determined by XDG_CURRENT_DESKTOP environment variable). If the desktop is Unity, it should default to visible at all times.
Auto-hiding the system tray icon will be prevented on the Unity desktop, in KDE Applications version 17.04 (due for release in April). Commit c522b0d090d63e67be8faa7320920f02f23f04e6.