What does it mean when a pathway is not identified within a sample?

[RunyuXia]

Hi! I'm running CellChat on individual samples, and I've noticed that certain signaling pathways are only identified in specific samples. When I try to extract these pathways for some samples, CellChat indicates that the signaling pathway doesn't exist. Could you explain what this means and how it differs from a situation where the probability is equal to 0?