I have been investigating this and I think I may know what is causing a problem with it. The capacitor and inductor tied to the output transistors is not filtering this to an AC sine wave. The capacitors and inductors in Multisim are considered ideal meaning that they have no internal resistance. Couple this with the fact you are switching with a pulsing DC. So it appears to me that without this internal resistance in a series configuration with a DC pulse, the simulator is treating them both as short circuits. You would probably get the same results even with those two components removed from the circuit.
The way it is supposed to work is that this series combination should filter this to an AC waveform and also provide an amplification boost to that AC waveform due to the reactances. But if Multisim is ignoring this reactance because of the DC switching, then that is why it will never work in the simulator.
The above is what I have observed and may not necessarily be the exact cause of the problem, but this is what I have observed. I believe it to be correct, but I have been known to be wrong before.
I hope this helps
