Stroke or play on? Good or bad call by the umpire?

This action happened during a game for the EHL between the teams of Uhlenhorster HC and HC Bleomendaal. After a perfect pass through, Brouwer (Bloemendaal) was left face to face with the keeper who stretches out his leg and touches the ball however, the opponents is knocked down to the ground. Blomenedaal’s crowd was demaning a penalty stroke but the umpire said play on, what are your thoughts on this one?