Probably you weren’t winning 99% after the 3 passes and it lived then. That’s the risk of playing the OGS triple-pass Go variant! OGS invents new Go variant!
If you are ahead and past move 120*, rather than playing moves to try to win, you can take a gamble and pass: if your opponent doesn’t have a ko threat type move big enough to drop your lead below a KataGo estimate of 99% after you pass following the ko threat, they follow up on the threat and you pass again, then you win. But be warned, if you are still winning after the 3 passes, but only 95%, you don’t win and have to keep playing
*180 now