If your patio heater is failing to stay lit it could be that the thermocouple needs to be adjusted or replaced. Please find the below Youtube videos on opening up the heater head and replacing the thermocouple. Before replacing you can try spraying with compressed air the tubes once the head is open as spiders can build nests inside stopping the flow of gas. You can also check the thermocouple valve to make sure it isn't loose or too tight while also verifying the thermocouple wire connection. (Disconnect and reconnect the wire)
The height of the thermocouple can also be adjusted up closer to the burner flame.