The DUE pinout diagram here;
Shows the SPI SCK on 13, MISO on 12 and MOSI on 11.
The Schematic and PCB design (dated 28\01\19) show that D13,D12,D11 are not connected to the ISP connector in the middle, which is clearly marked 'SPI' in the picture. This is where I am used to picking up SPI pins on a DUE.
Does the current DUE have the SPI pins on D13,D12,D11 ?