There are several potential reasons why your radiant heating system may not be working. One possibility is that the system is not properly installed. Another possibility is that there is a problem with the thermostat or with the valves that control the flow of hot water through the system. A third possibility is that there is a problem with the boiler or with the piping in your home. If you are unsure what might be causing the problem, it might be best to consult a professional to diagnose and fix the issue.