05-15-2012 11:26 AM
To identify if the issue is specifically with your database, open the demo database (or create a new database) and create a test activity - see if the alarms window appears.
If it doesn't appear for the demo database, it is likely that the window is being displayed off-screen. Manually rebuilding the preference files should resolve this: KB Article 14770
05-15-2012 01:16 PM
Just to verify: are you saying that if you create a new activity, the alarm will display?
If it is just older activities that don't display the alarm, how old are the activities? I've tested (in 2012) back to 90 days and alarms will still generate. Create an activity in the past with an alarm to test.
If it will generate the alarm for the activity created in the past, it sounds like the alarms have been cleared. Once cleared, they will not reappear.