Update countdown timer software for team-building game

We are a teambuilding company focusing on escape games and IRL teambuilding activites.
For one of our Escape games, we have developed a software that shows leads on a big screen as well as enables the game-leader to have control over the game. This software was developed by a freelancer 3-4 years ago and now this freelancer is no longer operative here so we need to find someone that can help us update the software so it will work with newer versions of windows update, which is now an issue.