OTGW module: How force starting the heating of the Domestic Hot water

I’m using a Vaillant EcotecPlus boiler with a separate storage tank for the Domestic Hot Water.
I installed the Opentherm V33 module in the Vaillant. And this internal module is connected with the OTGW module I bought at Nodoshop. At this moment, I’m NOT using a Opentherm thermostat but an on/off thermostat.

In Home Assistant, I’m using the Opentherm integration. This works fine and give me several values.

From within Home Assistant, I can change the setpoint for the DHW with the service "set_hot_water_setpoint. But the Vaillant don’t start heating the DHW storage tank? What should I do to start the heating of the DHW?