Heating, Vaillant Combo Home Heating Systems?

Vaillant combo VUW SOE 280/2-5R3

Serial 51950080A Starts fine and running fine for hot water. The problem is heating, after initial startup heating pump will not stop running and heater will not start to heat water. When I turn on hot water in the sink or shower it switches fine to hot water and working normally. What could be the problem? Maybe in the program itself or some sensor does not working properly? Thanks