RW420 change language to ZPL

Here is my code:

string cpclData = "! 0 200 200 210 1\r\n"

                        + "TEXT 4 0 30 40 This is a CPCL test.\r\n"

                        + "FORM\r\n"

                        + "PRINT\r\n";

string zplData = "^XA^FO20,20^A0N,25,25^FDThis is a ZPL test.^FS^XZ";

ZebraPrinterConnection thePrinterConn = new BluetoothPrinterConnection(Mac);

theprinterConn.Open()

SGD.SET("device.languages", "ZPL", thePrinterConn);

thePrinterConn.Write(Encoding.Default.GetBytes(cpclData));

thePrinterConn.Write(Encoding.Default.GetBytes(zplData));

My printer prints only cpclData string.

On zplData there is an empty label.

When I read SGD.GET "device.languages" I got info, that "zpl" is set.

But when I use:

ZebraPrinter myPrinter = ZebraPrinterFactory.GetInstance(myConn);

PrinterLanguage myPrinterLanguage = myPrinter.GetPrinterControlLanguage();

I get CPCL. WHY ?