Hot water but no heating

I've recently moved into a flat. Up until now the system had worked great, the heating came on quickly and worked very well. But today I noticed the heating wasn't working, having looked online I checked the pressure and it had dropped down to near 0. I have repressurised it to 1.5 but the heating still won't work. The pump to the heating doesn't seem to be operating. The hot wate system is still fine.

Please can anyone give me a suggestion? It is a 9kW unit.

I forgot to mention that this is an Electramate2000. On the panel HL1 and HL2 have green lights, HL5 has a red light.

Hi I don;t know the in and outs fully of this system and don't recognise the HL indicator that you mentioned. This is a link to the manual for the Electromate 2000 http://www.gledhill-spares.net/documents/EM2000-Iss6.pdf

The man control board is a GT155 (or GD131) these can go faulty the typical symptoms are no red display the one that should say -on. Or all the green LED's on but outputs not working properly and/or the hot water pump running constantly. I have some videos on my website showing how the board works in a Boilermate 2000 most of which is relevant to the other systems it is used in including yours. https://murraymartin.yolasite.com/ The videos are at the bottom of the page. Regards Murray