No heating on a baxi 105he?

Hi I changed a faulty diverter valve on a baxi 105HE but when the heating is on nothing goes through the flow but the plate gets hot and so does the dhw pipe. I've got 227v at the pump and it's
spinning fine. I've checked the return filter and there doesn't seem to be any restriction even tho it looks as if it is. Any help would be great.