Aurelion sol's ult did no damage [gameplay]

So i was playing and when i ulted it did no damage but it did slow him, he even had that glowy effect you get when you get blasted by sol's ult, he confirmed it in chat, he was under turret with 150 hp and my ult should have done more than 300, he didnt use barrier, there wasnt a soraka in the game, he said in chat that my ult did 0 damage and so the bird man lived