Central Heating not turning on unless Hot Water is also on?

We just had the motorised Two-Port valve by the cylinder replaced. However, whenever we call for just the central heating, it does not come on. The only way to trigger the CH is to also switch on the HW at the programmer (we can switch off HW right after). When doing this, we however don't get HW and have to switch off CH (then the lever position opens for HW) and we get HW (The order matters) Will be testing whether calling for hot water only gives a similar issue. Please refer to the pictures below for our system: https://i.imgur.com/p2XGN5c.jpg https://i.imgur.com/gCa4QQK.jpg