Enemy left vision as I ulted as Mordekaiser caused neither of us to enter the shadow realm

Essentially what happened is that I clicked "R" on the Sion as he enters the bush, and we never enter the shadow realm. This caused my own ult to go on cooldown, however whenever I pinged the timer on my ultimate it would say ready to use even though it had the timer indicating it was on cooldown. My teammates could also see that my ultimate was not ready either. in the video you can clearly see the cast animation and the ult going on cooldown. Hope this gets looked into thanks!