The scenario that would lead to the plant's death is a lack of oxygen.
While the plant can survive for some time using the carbon dioxide it has accumulated, it will eventually consume all the oxygen in the sealed environment during respiration. Without oxygen, the plant cannot perform cellular respiration, which is vital for its survival.
It's also worth noting that if the plant can't access light for photosynthesis, it won't be able to produce sugars, but the immediate concern for survival in a sealed environment would be the lack of oxygen.