Cannot knock unconsciouss

so I want to stun the sleeping inn keeper, but if I crouch and press F the cursor only changes to some sort of cross and henry doesn’t do anything.
Next I tried to rob him. I was able to steal a few items, but the second attempt ends up always with victim noticing me, but he does not wake up! What is this?

Sounds like nothing a good, sharp axe can’t taken care of . . .