Water ingress in new built concrete block shed

Hi there,Looking for some help.
I recently got a concrete shed built with blocks...covered with pvc cladding on straps to the outside.
Wooden roof with felt and roof insulation inside
Ventilation either side of wall and in soffits
I have painted inside shed with masonary paint but the amount of water or condensation inside on walls since is ridiculous....really really bad....soaking,any idea of what could be causing it.
I have no idea how to solve problem any help would be greatly appreciated.