Thoroughly clean the area and fit specialist htg adhesive flashing to bridge the problem area.
Plastic conservatory roof leaking.
For what it counts and based on your initial message you may not need to replace the polycarbonate just the rubber seals and maybe underside spacer strips if any.
A conservatory roof leaking in centre could be due to a slipped or incorrectly fitted roof panel a cracked glazing unit or a perished seal.
Leak through the roof vent.
Our advice would be to get a conservatory roof specialist to visit and check out the scope of the repair work.
Leak below roof vent due to failed poor mutin bar seal above or below.