It is very common for goalkeepers to save a ball and not show any sign of having saved it. I often ask them “did you save it or was it a goal?” to try to make them see that they have to show their happiness for the goalkeeper’s final success.
Celebrating positive actions helps us to reinforce the goalkeepers’ self-esteem, make them feel part of the game, encourage the team, involve the public, etc. Therefore, we must encourage them to make some kind of gesture when they stop the ball.
There will be goalkeepers who do this innately and there will be others with whom we will have to work on it. We will start with small private gestures between the coach and the goalkeeper (or with the other goalkeeper on the bench) until we get them to externalise this happiness.