Vorniclex stops the "QQ" mana tap out ability from functioning.
If you have a lot of lands, it triggers the response from Vorniclex individually to the first land tapping and cancels out the rest of the lands tapping. This doesn't count against the play timer so you end up timing out and the mana expires since it pushes you into the next phase.
QQ should put all the land taps on the stack and all the Vorniclex triggers with them. I lost mana multiple times when trying to tap out for spells with X in the casting cost.
I wanted to use QQ because I had forests as creatures and other creatures that tapped for mana that I wanted to remain untapped as blockers so I could not just play the card and submit a number for X.
Specific combo: Nissa, who shakes the world + Argothian Uprooting with lots of forests from Mythweaver Poq & Traverse the Outlands