AD5270 stays in midscale

Hello, i have an application, where the AD5270 should set a voltage inside a LDO-circuit, but the Wiper-position doesnt change from the mid-scale. The commands i sent are:

0x1C03
0x0407(random data, to test the RDAC)

The SIMO, SCLK, and the SYNC signals are measured right at the Pins of the AD5270. In the figure the red signal is SYNC, the yellow one is the Clock, the green one is the DIN and the blue one is the SDO. I also tested the code 0x2400, to set the software shutdown to normal, which didnt work either.

Is there anything i have missed out to get the RDAC working?

Thanks in advance.