Kalista Oath-Sworn unable to rebind??

Not sure if this s a bug or something they changed. Had my lane partner and the person i used my oath-sworn ability on leave 5 minutes into the game and after was unable to select another person to use oath-sworn on effectively taking away a huge chunk of damage and my ult. I bought a new spear but when i tried to bind i would get the bell toll then nothing would happen.