Not always—sometimes someone stops talking to you. They think the reason is utterly obvious, but it was really just unfounded gossip or something totally random that didn’t stick with you at all. You may have no clue.
On the other hand, sometimes you have a pretty good idea. And if you have no clue, you can usually do something to get clued in.
However, you may wish to revisit your wording of this question to elaborate as to what you actually wanted to know.