Tightrope Terror is a minigame on Game Show Island (part of the May Day Tour / May Day Maze event in Animal Crossing: New Horizons, May 1–7 annually).
Talk to Rover at airport during May 1–7 → "May Day tour" → get ticket → fly to island → navigate maze → Tightrope Terror is one section.
Tip: If struggling, close software → re-enter → maze layout rerolls (tightrope length may change).