GAC disappearing buttons

While in 3v3 GAC I was playing with SLKR/KRU/Sith Troopers vs LV/Maul/RG. Maul went down, then ST. LV and RG were in low yellow HP. I was at full HP and some protection. I had full Ult and hit the button to activate....

And nothing. No animation. No movement. No buttons on the lower UI. I still had the settings, auto, etc. at the top left. But no matter what I did it would no progress the battle. The time still counted down. However, once it reached zero the battle still just stayed locked. I had to reset the client and the battle was as if I had retreated.