Both wav and wma sounds formats should play ok (the program basically supports any sounds supported by your operating system eg mp3)
You said the one for 7:30am worked. Was it playing the wma or wav format?
What was the sound format for the one that did not play?
Is there any chance kirby alarm pro was not running when the alarm that did not play was due to be executed?
If so perhaps you have ticked the "Skip Missed Alarms" alarm setting.
Would you be able to try it again. Perhaps set up a test alarm and see if it plays ok.
The other thing to check is the alarm log to see if the alarm was executed.