How do you know that someone doesn’t want to talk? If you have tried to approach them and they have declined or pulled away, then see answer above!
Make sure you’re not assuming that someone doesn’t want to talk based on ambiguous information e.g. body language. Sometimes people might seem closed off or withdrawn but might really like the opportunity to talk, they just don’t know how to start a conversation.
Can you create opportunities in your workplace for people to come together informally e.g. team lunches, putting informal catch up time on the agenda for meetings? This may give an opportunity for someone to talk when they might not feel able to in more formal interactions.