Crossing interpersonal boundaries…

So my question for today is this:

How are you supposed to know if you’ve crossed a line with someone if they (a) never tell you, and (b) allow months to go by without any noticeable indication that something is wrong?

Events from this afternoon have left me seriously confused and concerned. 

EDIT: I realize there is a lack of details here, and no real context. TBH, I don’t entirely know what the actual situation is - this is something that came at me out of nowhere from a third party, not the person in question. I’ll have to post an update once I have more pieces of the puzzle.