Repair tape maybe your best best if you ve seen that the cause of the leak is a physical hole to your plastic conservatory roof.
Plastic conservatory roof leaking.
Leak through the roof vent.
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 below roof vent due to failed poor mutin bar seal above or below.
Thoroughly clean the area and fit specialist htg adhesive flashing to bridge the problem area.