ZQ510 printer. Mag card reader not found.

HI i'm working with a ZQ510 printer and I'm trying to read some card info with the card reader in an android software I'm making using Xamarin Android.

If i use the Zebra Setup Utilities software, I'm able to send this command to the printer "! U1 MCR 80 T1 T2 T3" and the printer wait for a card to read which is fine.

If i send the same command by code using this method :

string magCardCommand = "\r\n! U1 MCR 80 T1 T2 T3\r\n";

byte[] result = printer.Connection.SendAndWaitForResponse(Encoding.ASCII.GetBytes(magCardCommand ), 500, 500, "");

once again, the printer wait for a card to read.

But when i try to use the MagCardReader class from the Zebra.Sdk.Device package using this line of code

IMagCardReader magCardReader = MagCardReaderFactory.Create(printer);

I receive null and from what I saw from the API it means that the card reader isn't found.

Is there something I'm missing ?