Audio recording VS1033d

Hello there, this is my first post.
What i try to do is a audio recording with the sparkfun Vs1033d breakout borad and save recorded data to sd-card.
I allready solved the “Spi Problem” and did so by writing a Software Spi. I studied the Vs1033d datasheet and tried to implement the VS1033d ADPCM recording example, but still i cant get any signals at the lineIn pin of Vs1033d , because its buffer is full off zeroes, thats what my debug told me. I tried the MCN/MICP Pins as well, same result → only zeroes.
You can poll a register of Vs1033d named : SCI_HDAT1 ,this indicates the number of words available in buffer. So the buffer has data, well but only zeroes. Has anybody had some success with ADPCM audio recording with VS1033d ?

Attached is my modified Vs1033d Datasheet for comfortable reading and my Arduino code

VS1033D-Datasheet.pdf (725 KB)

RecordTest.pde (24.3 KB)