Nicholson and almost all the other quality file and rasp makers (Simmonds, Grobet) have moved their manufacturing operations to lower labor cost sites outside the US, Western Europe, etc.). Example per TFWW - Nicholson makes their #49 and #50 cabinetmaker's rasps and saw files in Brazil and most mill files in Mexico. Although some sellers claim they are beginning to see some improvement, most despaired of satisfying their customers and moved to Grobet/Grobet USA or other suppliers and have been dealing with further quality issues or more offshoring.
The solution for those that need a couple files from time to time is to buy new old stock Nicholson as linked in my post; for those that need a steady supply of files, other sources such as Italy's Corradi (check eBay or order direct, as they have no full line US importer/dealer) may be the best option, given NOS tools carry a 100%-150% premium on price. Selected Pferd (German) files are also available and stack up well compared with NOS Nicholsons for stuff like cabinet files, but the shear range of stuff from Nicholson has not been duplicated to my knowledge.