Auto Attack Bug [Gameplay]

I am having an issue with my champion and auto attacking. It seems that after killing one unit (or the unit dying due to other causes) my champion stops auto attacking. He will not continue on to attack another unit within range. This makes for very annoying situations in the jungle or with AD champs, where I have to click on each unit I want to kill. Could you help me fix this issue? Thank you very much for your time.

I do not have steps to reproduce, because I don't know how it happened and it is always happening now. I run League on a Macbook Pro.