Alarm clock does not ring

Q : Even though activated the alarm clock on Galaxy S5, the alarm doesn’t ring. What’s the problem?

A : If you had ever switched on the Emergency mode or Ultra power saving mode, alarm on your Galaxy S5 may not ring normally.
At that time, please restart your Galaxy S5, and then alarm activated will ring again.
Additionally, Samsung already know the issue and will soon support the improved binary via Kies or FOTA.