replacing a manifold

[gingerbloke]

help needed urgently. i've got a combi boiler sealed system the rads are fed with 10mm micro bore from a manifold. the upstairs manifold which serve four rads started to leek and had to be replaced from a copper one to two plastic ones ever since then the rads upstairs won't get hot both the flow and return pipe are hot and so is one pipe feeding each rad off one of the manifolds the four pipes from the other manifold is cold.

please help what have i done wrong.

 

[seco services]

what is the cold manifold on the return side ?

 

[gingerbloke]

the flow and return pipes upstairs originally had the manifold linking the two together which was a copper one. but you can't get a copper manifold for love of money so i had to use to plastic ones as there bigger and i'm restricted for space i had to put them next to each other on the one side the plpe then goes round and connects to the return.