Would you advice a combi boiler have hot water but no heating

[Tie]

Hi all,

I am new here, what to get some advice for a combi boiler have hot water but no heating.

This is first run CH after the summer. Radiators are cold. The vaillant VCWGB 242EH bit old one just got diverter valve changed on last winner.

I can hear the fan running. the after setup high temperature on Thermostatic (25 degrees). the thermostatic try to kick boiler to work just fan running but no fireing gas.
pressure is 2

I have turned on and off boiler few times and changed batteries on thermostatic.
the temperature knob under the boiler has never been touched.

Thanks.