Downstairs heating not coming on

sdc1985

Hi I've my heating on 2 zones and switched by eph detach pro v221p motorised valves.

Our boiler (potterton 4 yrs old) had its pressure vessel replaced yesterday.

Since then my downstairs zone will not come on. The boiler is reacting and the motorised valve seems to be turning but still no heat. I swapped the 2 motorised valves around but still the same with upstairs working with both valves and downstairs not on both.

Any advice would be great.