The company who laid the floor are at fault. Might need to go down the inspection route of floorskills or the NICF The floor should have been tested and checked by the flooring company and either removed the old screed compound and put down an epoxy Dpm then prime and a smoothing compound over that.
https://www.floorskills.co.uk/inspections/ https://nicfltd.org.uk/NICF-Directory-Member-Info.php?ref=fa23f3a7-04da-4378-8b2f-2ad3bb15df55
