This is the 6461st most frequent Korean word.
없으니
"없으니" means "because there is not" or "since there isn't."
In this sentence, '없으니' indicates the absence of ingredients as a reason for the inability to cook.
재료가 없으니 요리를 할 수 없어요.
Since there are no ingredients, I cannot cook.
Here, '없으니' is used to express the lack of time as a reason for the urgency.
시간이 없으니 빨리 가야 해요.
Since there is no time, we need to go quickly.
'없으니' in this context explains the lack of seats as a cause for the given instruction.