Cursor won't show when I do an attack

I have this problem occurring in my matches lately. Whenever I press Q, W, E, R or any other key to land an attack, the blue cursor thing vanishes and I can't place my attack unless I select a specific target. Normally I would simply hit a key and then the blue attack cursor (blue arrow or a blue circle would) would show and bam, there's my attack. But because of this issue I'm having i am not able to find my target properly and this makes LoL hard to play. If anyone knows what the solution is, please let me know.