Step-by-step explanation:
Green house effect occurs when the wavelenght of the infrared radiation in the incident solar radiation, looses some of its energy on reflection from the earth surface, making it longer and unable to pass through the greenhouse gases that act like a blanket around the earth.
The reflected radiation has a longer wavelenght because it looses energy to the earth as heat; leaving it with a new wavelenght too long to go through the greenhouse gases.
The jar envoirment does not provide the earth-like material that can absorbs some of the energy of the incident radiation so it goes out with relatively the same energy. Also, the refractive index of the green house gases and the glass used in the lab might not be the same so modeling it with a glass might not produce the same effect.
Finally, the light source used might not contain enough infrared energy as an incident solar radiation.