Samsung Galaxy S9- Pin screen- start delayed- no alarm

[r.mark.1632@gmail.com]

I depend on my phone's daily alarm, but about weekly, I find my alarm did not sound and see my phone is stuck on the PIN screen despite the fact the phone was connected to a charger overnight. I am unaware the battery had dropped to 0% since the phone had 40% or more power when I connected the charger overnight. Any clues how I can resolve this to ensure my daily alarm functions as expected? Thanks!