The instrumentation amplifire circuit in the examples has unbalanced inputs one of which terminals is connected to GND. Unfortunately, if it is not connected, this simulator dosen't work.
This circuit shows how to think about the instrumentation amplifire with balanced inputs. Simply devide the input voltage to two, and devide the resistor in the center to two. Connect both centers. Then this simulator works (Figure in the left). Because it's same as two non-inverting amplifires. But please remember, there is no current on the line that connects both centers of the input voltage and the resistor. So, it's same as when they are not connected.
Unfortunately, if cut the line of that, this simulator doesn't work (Figure in the right).
