It's some kind of account related bug. I have a similar problem on this account where I can only ping things using TAB, everything else on my user interface can't be pinged (which I learned the hard way by constantly using my items when I was really just trying to ping them). When I switch to a different account, the problem vanishes completely and I can ping everything normally. I've tried un-installing and re-installing the game, and everything went back to exactly how it was before I removed League.
I don't think there is anyway to fix the problem, seems related to something Riot stores on either your computer or their server for settings. The problem is also cross-computer for me as well since it doesn't matter which computer I install League on, this account always has the same problem where I can only ping things with TAB.