It's the hook you just missed. Almost every sentence hands you a detail to pick up — follow it, then give something of your own back. Seven days, one habit at a time.
'We were in Lisbon for my sister's wedding' contains three openings. Missing them — not lacking questions — is what produces the pause where you both look for something else to say.
It's the standard advice and it makes conversations worse. Question, answer, new question, answer — people feel it before they can name it, and they stop offering much.
People open up roughly in proportion to what they receive. A conversation where only one person shares stops feeling like a conversation, however good the questions are.
Which usually means the material was there and the retrieval was slow — a different problem from having nothing to say, and one that responds to a habit rather than a phrase list.