Hello, Victor.
I am sorry you are having trouble getting the Maestro to work with your new Raspberry Pi. We have not tested the Maestro on Windows 10 IoT Core, but we have heard reports from other customers getting it to work.
You should make sure the serial mode of the Maestro is set to “USB Dual Port”. You mentioned trying the “UART, fixed baud rate” mode but that mode will not work with the C# code you posted. (I’m assuming that you want to control the Maestro via its USB connection and not its RX pin.)
Since you are using the Pololu protocol and specifying a device number of 12 (0x0C), you should make sure that your Maestro’s device number is actually set to 12 (which is the default). You should also make sure there is a servo plugged into channel 0, and that the servo on channel 0 works when you control the Maestro with the Maestro Control Center.
The Maestro provides two USB virtual COM ports: you should check that your program is connecting to the Maestro’s command port. You should be able to see the two ports listed in your Device Manager.
I also noticed that you are sending two “Set Target” commands back to back, with no delay between them. If the servo is already in the position indicated by the second command, you might not notice any movement. You might consider adding a delay between those commands.
Please let me know if you continue to have trouble or have further questions.
–David