Therefore, "zero gravity" is not really a point where gravity "stops working."
It's the craft falling and staying in motion because there is no drag to stop it. And it will continue in motion like this, called "orbit," until something applies "brakes" to slow it down.
The balloon however, was not propelled by a rocket. It has no velocity, no speed. Therefore, it will ascend until the temps or pressure burst the balloon and it will immediately fall back to earth.
It falls back to earth simply due to the fact that the ring weighs more than the vacuum. It does not fall due to a mysterious force called gravity.
And there is no "point" in altitude which one can cross over and suddenly become "weightless."
This photo is a simple proof there is no such thing as gravity.