Hello!
I'm level 13 with arcane missiles rank 1.
When i'm casting arcane missiles it just channels without any missiles coming out, when i first learned the skill missiles would come out 30% of the time but now my character is just channeling without any actual missiles coming out.
Just tested rank 1 arcane missiles on my level 80 mage on a training dummy. The skill seems to be working fine. It's probably you were hit by a mob or something and the pushback prevented the missiles from coming out.