You have the syntax wrong, AddPrinterConnection and SetDefaultPrinter uses different syntax.

SetDefaultPrinter uses the printer name and not the printer path name, see below.


SetDefaultPrinter ("<printer name>")

printer name = the fully qualified name (include the double backslashes and the server name) for the printer to be set as default


AddPrinterConnection ("<printerpath>")

printerpath = UNC path to printer name ("\\server\printer name") or share name ("\\server\printer share name")